Superseded by the iPhone 4S but freshly equipped with the very latest version of Apple's iOS software, the iPhone 4 remains a formidable challenger in the mobile arena.
It has a super-sharp retina display, a 1GHz processor and has been manufactured in 8GB, 16GB and 32GB variants. You can pick up the 8GB model for £400 on a pay as you go deal, with SIM-free prices coming in slightly higher at £430. The iPhone 4 is available for free on a monthly contract from £25.
In summer 2010, the iPhone 4 was the hottest name on the mobile scene. It had the looks, the software and the desirability factor. With the exception of a few irksome issues with its network reception, nothing but positive things were being written about it.
Today, the story is slightly different. The more powerful iPhone 4S is Apple's new crown prince. It has features that have been withheld from its older sibling -- virtual assistant Siri being the most notable.
While existing iPhone 4 owners will be pleased that their devices have been upgraded promptly to iOS 5, it's trickier recommending this handset to new customers. The iPhone 4 sits awkwardly in the middle of Apple's current mobile catalogue, sandwiched between the cheap-and-cheerful 3GS and the all-singing, all-dancing 4S.
It's still a highly recommended phone, however. If you can grab one at a decent price SIM-free, then we'd advise you to do so. However, if you can afford it, you'd be better off stumping up the extra cash for the newer iPhone 4S.
As well as updating the doddery old 3GS to iOS 5, Apple has delivered its latest and greatest software to iPhone 4 users. Key features were missing from iOS 5 when the iPhone 3GS recently received its update. We're sad to report that the same story applies with the iPhone 4.
It's to be expected -- after all, Apple wouldn't sell so many iPhone 4S handsets if the older hardware got the exact same features. What does make the cut is so fantastic that you're unlikely to be too disgruntled.
If you're a long-standing iPhone owner, you'll no doubt have endured a few debates with Android lovers over the merits of your respective platforms. The topic of notifications usually gets dragged up during these exchanges, and until recently, it was generally accepted that Google's way of handling such alerts was superior to Apple's.
Not any more. iOS 5 boasts a completely re-engineered notifications system, which borrows ideas from Android whilst applying that traditional Apple lick of paint.
New to iOS 5 is the Notifications Area, which can be pulled down from the screen, just like the Android notification bar. In this area you'll find all of your alerts, be they text messages, emails or calendar appointments.You can select which notifications are pushed to this area from a separate settings menu, should you find the flood of alerts too overbearing.
Die-hard traditionalists can revert back to the old-fashioned pop-up notifications if they wish. It's even possible to mix and match, so you have emails appearing in the notifications area and text messages flashing up on the screen as a pop-up.
It's a surprisingly customisable arrangement and caters for all tastes. If you're an Android user moving to iPhone, you'll be very much at home.
One of the biggest complaints iPhone users have had since the device launched in 2007 is its dependency on iTunes. Although Apple enabled us to download apps and games directly to our phones many moons ago, you still need to plug your iPhone into your PC to install updates and back up existing downloads.
This outdated procedure is removed in iOS 5, unshackling the iPhone and bringing it more in line with Android and Windows Phone. Firmware updates can now be installed over the air, which means you don't need to tether your phone to your PC when the next big iOS update is released.
Better still, you can now re-download purchased applications directly from your handset. The App Store remembers which apps and games you've previously installed. It even displays a list of them so you can effortlessly reacquaint yourself with some vintage classics.
iCloud is useful in many other ways too. Apple gives every iOS users 5GB of personal storage, into which they can upload music, photos and other data. You can then pull this information down to your device without having it clogging up your phone's internal storage.
If you switch phones or -- heaven forbid -- lose your precious handset, iCloud handles backups of your device. If the 5GB isn't enough, you can purchase larger storage space directly through your phone.
One big plus that Android has over iOS is the fact that you can share pretty much anything using the built-in share menu.
So if you're looking at a photo, you can click the share option and a list of all relevant apps -- such as email, text message, Facebook and Twitter -- is displayed. This allows you to effortlessly post your image. Whenever you install a new app with sharing capabilities, it's added to this list.
While iOS 5 doesn't quite take the sharing ethos that far, it does at least allow you to post directly to Twitter. That means no more having to fire up your stand-alone Twitter client to post images or links -- you can do it directly from within the iOS 5 interface.
This is a real time-saver and makes things much more intuitive. Our only gripe is that Apple hasn't seen fit to include quick sharing to more networks, but we imagine that future updates to iOS 5 will bring what we desire.
Another new addition in iOS 5 is Newsstand. This is basically Apple's effort to reinvigorate the ailing magazine industry. Early accounts seem to suggest that it's working, to a certain degree.
Newsstand is the kind of app that is more suited to a large-screen tablet device, like the iPad 2.
Still, the iPhone 4's 640x960-pixel high-resolution screen does at least make it easy to read text. As such, Newsstand makes more sense on this phone than it did on the 3GS, which only has a 320x480-pixel display.
One of the few reasons to still own a BlackBerry device these days is RIM's excellent BlackBerry Messenger service. This system allows users to keep in touch over their phone's data network, rather than having to use up their monthly allowance of text messages.
Apple has incorporated a similar feature into its latest operating system, but typically, it's even more user-friendly. In fact, it's so well-realised that many people may not even notice that they're using it and not simply text messaging.
Instead of having a separate iMessage application, iOS 5 simply detects people on your contact list that are capable of receiving iMessage communication. You still use the standard text messaging application, but iMessages are displayed in a different colour.
By keeping iMessage as part of the standard iOS messaging service, Apple has avoided the annoyance of having to skip between apps when receiving the two different message types.
Sadly, not all of iOS 5's amazing features could be shoehorned into the iPhone 4. The most obvious casualty is Siri, the famous voice-controlled personal assistant found on the iPhone 4S.
Easily one of the biggest advancements in iOS 5, Siri has been at the forefront of Apple's promotional campaign for the iPhone 4S, so it's frustrating to see it absent from the iPhone 4. This is especially true when you consider that it's been proven that the device is perfectly capable of hosting the service.
This is less of a blow than the removal of Siri, as there are plenty of other ways of achieving the same result which can be downloaded from the App Store.
Despite being over a year old, the iPhone 4 (and its successor, the iPhone 4S, which shares the same external design), is one of the best-looking phones on the market. Even many staunch anti-Apple types will admit that no other device comes close -- you only have to cradle it in your palm for a few seconds to fall in love with the handset.
The iPhone 4 is built from high-quality materials too. There's not a trace of cheap plastic in sight. The front and back are chemically-strengthened glass, while a metal strip runs around the sides. This also serves as a dual antenna, providing all of the handset's wireless connectivity. This design is ingenious, but also causes some bothersome issues -- which we will cover shortly.
The glass feels robust enough. Apple is insistent that it's more durable than any other available material. It's certainly capable of coping with everyday use, but from personal experience we can state that it is highly susceptible to scratches and marks.
It's also been illustrated that the iPhone 4's design doesn't cope all too well when dropped -- the glass (unsurprisingly) tends to crack, creating a phone that is a lot less appealing to the eye. You'll almost certainly want to invest in some kind of case to guard against such an unfortunate eventuality.
Another reason to grab a case is the antenna issue we alluded to earlier. Shortly after the launch of the iPhone 4 in 2010, scare stories emerged of a Death Grip problem -- users were finding that just holding their shiny new iPhone was enough to cause the signal strength to drop out.
As the scandal intensified, the issue was traced to the way in which the case was designed. The dual antennas are separated by two thin pieces of plastic; holding the phone can bridge the gap between them, reducing the signal strength.
How badly this issue will impact you personally is hard to say. Many people have reported that they see no degradation in network strength when holding the handset. Using a case almost completely solves the problem, but you may never even notice it in the first place.
Another thing to note is that the iPhone 4's 3.5-inch screen means that it's a lot more compact than rival Android blowers. Handsets like the Samsung Galaxy S2 and Galaxy Nexus positively dwarf Apple's phone, but it's hard to deny that the iPhone 4 fits snugly in the palm, with all areas of the screen easily reachable with your thumb.
Conversely, the aforementioned Android big-screen behemoths require both of your hands to operate successfully.
When the iPhone 4 launched 18 months ago, its retina display caused jaws to drop. Unparalleled pixel density and bold image quality made it the screen of choice for mobile connoisseurs. Even though Samsung has upped its game with the recent Galaxy Nexus 720p HD display, the iPhone 4 still holds its own.
The 640x960-pixel resolution delivers 330 pixels per inch, which means that individual pixels are practically invisible to the naked eye. Technical mumbo-jumbo aside, what you need to know here is that image quality is absolutely top-notch.
Although Samsung's Super AMOLED Plus screen technology provides deeper blacks and bolder colours, the iPhone 4's LED backlit panel still generates a world-class picture. Brightness is decent and colours are striking.
Enabling auto-brightness naturally diminishes the impact of the display, but it's nowhere near as aggressive as what we've witnessed on handsets like the Galaxy Nexus.
Although Android is arguably driving the market when it comes to processing power, many devices running Google's versatile OS struggle to make the best use of the muscle they're given.
A new breed of dual-core handsets may be making slow responsiveness on Android a thing of the past, but there are still an awful lot of phones on the market with single-core, 1GHz processors that suffer from stuttering and unresponsive moments.
Compare that to the iPhone 4, which is equipped with a single-core Apple A4 chip running at 1GHz. Even with the increased demands of iOS 5, the iPhone 4 rarely feels as if it's straining under the weight, and it's only when you have multiple processes running alongside each other that it starts to lag a little.
The iPhone originally came in 16GB and 32GB variants, with the 8GB version arriving slightly later on. The internal storage of the phone is shared between your apps, games, movies, photos, music and podcasts. If you're planning on using the iPhone as your primary media player, you'll want to opt for the larger version.
This is because unlike many Android handsets, you cannot expand the internal storage of the iPhone 4 via microSD cards.
The iPhone 4's camera is a massive step up from the one seen on the 3GS. The most obvious change is a jump from 3 to 5 megapixels, as well as the addition of that all-important LED flash. Owners of 3GS handsets will know all too well how difficult it was to shoot in low light using that phone, so this advancement is very welcome indeed.
A few enhancements with iOS 5 make image capture on the iPhone 4 even more appealing. You can now overlay a grid on the screen to get the perfect shot, and it's possible to quickly access the camera application from the lock screen by double-tapping the Home button.
Auto-focus and nippy performance allow you to grab treasured moments with ease. The quality of the resultant images is great. Colours are realistic and unless you make a pig's ear of composing the shot, over-exposure is rarely an issue.
The iPhone 4 has a front-facing camera so video calls are possible. Using Apple's FaceTime software you can converse with friends and family over a Wi-Fi connection.
The service is rendered with Apple's typically assured brilliance, but FaceTime is less impressive than it was over a year ago. Google's phones now have Talk and Google+ hangouts, so the game has most definitely changed up a gear.
Finally, it should be noted that the iPhone 4 is capable of capturing video at 720p -- again, this is a step up from what the 3GS was capable of, but falls short of the 1080p recording the 4S boasts.
As we mentioned before, that fantastic retina display makes the ideal viewing platform for detailed web pages. Text is rendered with astonishing clarity and images look wonderful.
You can use pinch-to-zoom commands to get a closer look at particularly content-rich sites. Navigating around pages is smooth and mostly lag-free.
With this being an Apple device, you'll naturally find no trace of Adobe Flash support -- this is unquestionably one of the main reasons the iPhone 4's Safari browser is so quick. Flash is becoming less important on mobile devices now anyway, and even Adobe itself has stated that no future mobile versions will be released.
Given all the improvements and new features introduced in iOS 5, it would be incredibly naive to expect the iPhone's 1,420mAh battery to last as long as it did with iOS 4. With iCloud sync, Find my iPhone and other new elements enabled, that pool of juice is getting sucked by a lot of new features.
Even so, there have been reports that the new operating system drains the battery with alarming speed, although we personally didn't notice a massive change when compared to iOS 4.
Apple is working on a fix that apparently solves the battery drain problem experienced by some users. But when all is said and done, you have to expect some trade-off for all of the new toys that iOS 5 brings with it.
Environmentally-minded folk will be annoyed to learn that the iPhone 4S does not contain a user-serviceable battery. The unit is completely sealed, and the only way to replace the power cell is to return the device to Apple and pay a hefty charge.
There's no doubt about it -- iOS 5 makes the already impressive iPhone 4 even better. The new features are fantastic and genuinely improve usability and enrich your experience.
While it's slightly disappointing that Siri hasn't come along for the ride, it's not a massive loss. The witty voice assistant may be one of the main improvements of iOS 5 from a marketing perspective, but we'd argue that iCloud, notifications and iMessage are actually more useful on a day-to-day basis.
Putting aside iOS 5 for a moment, the iPhone 4 remains a solid device -- even after over a year of availability. Granted, its single-core processor has been left in the dust by dual-core Android phones like the Samsung Galaxy S2 and HTC Sensation XE, but Apple has proven time and time again that raw specifications are irrelevant as long as the user experience is slick and intuitive.
However, despite the positives, the iPhone 4 finds itself in a rather unusual position. If you're new to iOS and are shopping on a tight budget, then you may be better off choosing the cheaper iPhone 3GS, which has lesser specs but has been successfully upgraded to iOS 5.
If money isn't an issue, then it's arguably a better idea to pick the newer iPhone 4S over the iPhone 4 -- the latter will set you back around £430 for a SIM-free version, whereas the 4S is only slightly more expensive at £500.
Still, many networks will be offering the iPhone 4 on cheaper contracts these days. If you're about to upgrade but don't relish the thought of paying through the nose for the 4S, this Siri-less alternative could be just the ticket. In fact, no one need ever know that you took the cheaper option, as both phones look identical from the outside.