Visually identical to the previous iPhone 4, all the new goodies to be found on Apple's latest smart phone are lurking beneath the surface, in the form of clever new software and improved hardware. But is a little tinkering under the hood enough to keep Apple on top, or are you better off this time around with an Android mobile?
The iPhone 4S is the pinnacle of smart phone excellence, but it's not as far ahead of the curve as the iPhone 4 was when it launched last year.
So if you own an iPhone 3G, 3GS or an older mobile, the iPhone 4S is a tremendously tempting option. If you do upgrade, the step-up in processing power, camera tech and especially the pin-sharp retina display will have you gawking at your mobile like a child who's found his favourite flavour crayon.
If you already own an iPhone 4 or high-end Android smart phone such as the Samsung Galaxy S2 or the HTC Sensation, however, the decision is much trickier. Voice recognition, a snappier processor and an improved camera are the shiniest lures, and we don't think they're shiny enough to warrant spending £500.
If you already own an iPhone 4, updating to iOS 5 will make your mobile feel refreshed, and will flood your phone with enough new features to boost its usefulness for the forseeable future.
We think the most important thing about the smart phone you buy is its operating system, because more than anything that determines what you can do with it. The iPhone 4S comes with iOS 5, the newest version of Apple's mobile operating system. So what do you get?
The basic iOS experience is unchanged for iOS 5. Apps are layered across homescreens in neat grids of 16 -- you swipe left and right to browse through them and tap on an app to open it, with your four most-used staying put at the bottom. Double-tap the home button and a taskbar pops up showing you all the apps that are running, and from here you can close them down or quickly skip back and forth between them.
The notification pane is new, however. Shamelessly lifted from Google's Android operating system, swiping down from the top of the screen will conjure up a panel displaying everything new that's happening on your mobile, including texts, email and calendar updates.
You can also stick some widgets into this pane, such as weather updates or stocks (we've still got no idea why every new gadget comes with a built-in stock-market ticker, but if you happen to own an impressive portfolio you might find it useful). Tapping on a notification will spirit you away to the relevant app, and there's a tiny x next to each one when you want to dismiss it.
The panel is attractive, simple enough to use, and it makes dealing with notifications from various apps much easier than on previous version of iOS. You can customise which apps appear in the notification pane and how they behave from the settings menu.
Notifications aren't restricted to that brand new panel. If you get a notification from one of your apps (a mention on Twitter or being tagged in a photo on Facebook, for example) while you're using the phone, a small box will roll down from the top of the screen letting you know what's what. It's much less intrusive than older versions of iOS, which required you to dismiss a distracting pop-up warning every time something happened.
Twitter is now baked into the software, so you can do things like tweet photos from your camera roll. That's great if you use Twitter, but if you don't, the option will likely just take up space and annoy you.
iOS 5 could save you a few pennies thanks to a service called iMessage. This is a messaging system exclusively for people who are using devices running iOS 5, and unlike text messages it's completely free. It's not a separate app -- the iPhone will figure out whether an iMessage is coming from someone in your contacts and display the messages in the same conversation view as your normal texts, but tinted blue so you can tell iMessages from SMS.
With iOS 5, Apple is finally releasing the iPhone from the fierce clutches of its desktop iTunes software, instead letting you store your email, contacts, calendars, reminders, Safari bookmarks, notes, documents and -- best of all -- photos online.
Dubbed iCloud, this slew of storage options ties almost everything on your iPhone to your Apple account, and backs up your iPhone wirelessly while your phone is locked and connected to the Internet over a Wi-Fi connection. In the future you'll also be able to update your iPhone's software wirelessly, without having to plug it into your computer.
One good thing about iCloud is that if you've got other iOS devices, you can get all your photos and data on to them wirelessly, downloading them from Apple's cloud storage once they've been uploaded to iCloud from one device. It also offers peace of mind, because if your mobile breaks it doesn't mean all your data is lost.
We had a few issues with iCloud in the short time it's been available, with an older iPhone 4 unable to access the service, with attempts yielding only unhelpful error messages. It seems to have settled down since though, so we think these issues were likely teething problems caused by Apple fans around the world rushing to join the service -- we will of course update this review to reflect our ongoing experiences with iCloud.
Other additions in iOS 5 include a camera shortcut from the lock screen (double-tap the home button) and a grid that appears over the camera's display to help you line up your photos, and a simple photo editor appears when you've taken a shot.
The volume up button now lets you take pictures while you're using the camera app, which cuts down on fumbled attempts to hit the on-screen capture button, and makes it easy to take self-shots because your digits can reach the mechanical button while the iPhone's display is turned away from you.
iOS has the best app offering of any operating system. There are hundreds of thousands available, and because Apple tests each app before making it ready for download, the quality in general is very high, with addictive, polished mobile games being a particular strong point.
iOS 5 is the best-looking version of iOS yet, and the polish that Apple has applied to every single menu and button means swooping around the iPhone 4S is a joy. It's worth noting, however, that with this host of new features, iOS is creeping away from what made it so appealing in the first place -- being so simple anyone could use it.
While still less complex than some rival operating systems, we can imagine someone new to iOS feeling flummoxed by the new notification pane, the options to tweet and print photos, or how exactly to access their stuff through iCloud.
The Settings app is still particularly weak as well -- diving into the settings menu every time you want to turn Wi-Fi on or off is way more hassle than it should be, and figuring out where things belong in the maze-like and ambiguous 'general' tab still induces headaches.
All the new features we mentioned above are available to the older iPhone 4 and iPhone 3GS as well as the iPhone 4S. So what reason is there to opt for the 4S?
Apple wants you to get excited over Siri, a voice-controlled assistant that lives exclusively on the iPhone 4S. You conjure this robotic PA by holding down the home button, and then barking an order into the 4S when the microphone icon appears.
Siri is more sophisticated than most voice-control apps, wrapping its bionic brain around complex phrases such as, "What's £50 in US dollars?" or, "Do I need a raincoat today?"
But in our experience, asking anything beyond those limited stock phrases is likely to yield disappointment, or public embarrassment. We were occasionally impressed -- we asked "Will I need an umbrella this time next week?" and Siri sussed the date in question and provided weather forecasts for the next seven days.
But for the most part, Siri just offered to perform Web searches for the questions we'd issued, and much of the time it didn't even manage to accurately figure out what we were saying. Ambient noise like other people chattering in our vicinity also made it hard for Siri to tell when we were finished issuing a command.
Here in the UK, Siri is even more hamstrung, because Apple doesn't have a deal with any UK providers of local information. So if Siri thinks you're trying to find a particular kind of shop or nearby locale, it'll tell you that it can only do that in the US. That's unhelpful and annoying.
Setting up calendar events proved to be a strong point for Siri, but that's one of the easiest tasks to perform using the Calendar app, with just a few pokes at the 4S' touchscreen.
Ultimately Siri impressed us too rarely, and we don't think its voice-recognition tech is accurate, reliable or useful enough to make it preferable to just opening other apps and sorting stuff out yourself. This is a shame, as we had high hopes for a voice-recognition tool that would blow every previous failed attempt out of the water.
So Siri isn't great, but the voice recognition tech on board the 4S comes into its own in other areas -- you can dictate text messages or notes, and unlike Siri, we can see this actually making your life easier.
The iPhone 4S packs a superior processor to the iPhone 4 in the shape of an A5 chip. Anecdotally it feels extremely slick, with apps opening quickly, menus sliding smoothly and rapid-fire typing proving snappy and responsive. Forget anecdotes though, let's get benchmarking.
While speedy, the 4S wasn't quite as fast as an iPad 2 running iOS 5, which scored a slightly more impressive 1,805.9.
We also ran a graphics test in the form of GLBenchmark 2.1, an app that runs a videogame-style 3D scenario and ranks the device's polygon-chucking ability. Here the iPhone 4S scored an impressive 6,568, handling the graphically intensive scenario with aplomb, and trouncing our iPhone 4's score of 1,621 (higher is better here).
So the iPhone 4S does deliver when it comes to speed, walloping its predecessor in terms of performance, and proving itself capable of handling some adventurous gaming. We can't wait to see new, ambitious apps that take advantage of this new processor.
The iPhone 4S packs a new 8-megapixel camera that's loaded with optic tech, including face-detection, backside illumination (chortle) and a new sensor. But does that fancy tech translate into decent snaps?
The answer is yes. The iPhone 4's 5-megapixel camera was one of the best in the business, and the 4S improves on that performance. We were really impressed with the dynamic range, with colours looking more natural and balanced than they do when taking photos with the iPhone 4.
There's the option to take some beautiful macro shots, thanks to the depth of field that this tiny snapper manages, while the 1080p video is crisp and colourful. We noticed a spot of rolling shutter making our video appear ever so slightly wobbly, but all things considered, the video capture on offer here is very impressive too.
The software is low on options, but blissfully simple to use, and the snappy processor comes into its own when taking photos -- you'll be able to snap photo after photo in rapid succession, and start recording movies rapidly without the 4S breaking a sweat.
Some killer camera tech combined with simple software and powerful hardware means this is the best smart phone camera we've ever used, and a compelling reason to upgrade to the 4S -- certainly more so than Siri. Look out for detailed comparisons with other leading camera phones over the next few days.
The iPhone 4S shoots video in 1080p, which is a step-up from the iPhone 4, which managed 720p video. We've embedded a short test video clip here so you can see how the iPhone 4S fares for yourself, but in our opinion, the footage this phone captures is very impressive.
There's a hint of rolling shutter, which is the effect that makes your video look wobbly when the camera moves. It's something we noticed on the iPhone 4 as well, and it's not too bad here. All things considered we think this could easily fill in for a proper camcorder when you go on holiday. Apple's iMovie app (sold seperately, £2.99) serves as a great little video editor too, bolstering the 4S' camcorder chops.
Anyone who's held an iPhone 4 will be au fait with the iPhone 4S' design, because it looks almost exactly the same as its predecessor. While it makes the iPhone 4 and the 4S hard to tell apart, the lack of a new look is not necessarily a bad thing, because this classy slab of gadgetry is still one of the best-looking phones in the business.
A slab of glass adorns the back of the 4S, while a rounded metal band along the edges lends this phone an industrial, modern look. Once the iPhone's button selection looked sparse -- the big 'home' button bang in the middle, circular volume buttons, a switch to turn the phone to silent and a lock key on the top are still all you get. In the last year rival manufacturers have opted for a similarly minimalist style, so the 4S doesn't look as singular as previous iPhones did at the time.
The volume buttons and mute switch have been altered slightly from the iPhone 4, with all three buttons moved down a few millimetres. As a result it's possible that iPhone 4 cases won't all fit the iPhone 4S, if the case is particularly snug around these keys. Most cases have a gap for all the buttons, so should be fine.
One gripe we'd level at the 4S is that it's very fragile. We've had over a year with the iPhone 4, and in that time we've seen more than our fair share of cracked casings and shattered screens. With the same design, the iPhone 4S will suffer just as much if you knock it off a table or leave it in the hands of a destructive toddler.
In conclusion, it's a shame that your mates and jealous commuters won't be able to tell immediately that you're carrying the latest tech, and the fragile casing could lead to tears, but this is still a deliciously classy phone, and one you should be proud to fill your pockets with.
Even the most sophisticated smart phone isn't much cop if it can't survive without sucking on its charging cable, so how does the 4S fare away from the mains?
With what we'd consider normal-to-heavy usage -- that is, brightness turned to full, intermittent Web browsing over both 3G and Wi-Fi, some time spent downloading and playing games and about 50 minutes of streaming YouTube video -- the 4S' battery ran down to 27 per cent from a full charge after 6 hours and 18 minutes.
We don't expect you'll end up using your 4S that much every day though. Based on our experiences, with moderate use the 4S will likely last you through to the end of the day. If you find the battery is draining too quickly, try turning off services you don't use, and checking which apps are monitoring your location in the settings menu, as this could be guzzling through your reserves.
We tried to burn through the 4S' battery as quickly as we could, by running graphically intensive 3D games Infinity Blade and Real Racing 2. The battery died after a little more than 3 hours, so consider that an approximate minimum life expectancy. We also noticed the 4S got very warm while it was running these games -- a sign that its processor is working hard.
These results are in line with our expectations -- we've yet to see a high-spec smart phone that can last more than a day or two away from the mains. We expect you'll need to charge the iPhone 4S every night to ensure it makes it through a full day, particularly if you're fond of downloading things or playing intensive games.
So far the 4S' battery appears to offer similar survivability to the iPhone 4. Indeed, the battery unit inside the 4S is very similar to that of its predecessor.
When the iPhone 4 was released it blew our socks clean off our feet, and caused rival manufacturers to scrabble frantically back to the drawing board, desperate to conjure up something equally cool and impressive. In short, it was way ahead of the curve.
The iPhone 4S is still ahead of the competition, but the gap has narrowed significantly, with Android and even Windows Phone devices becoming slowly more accessible and stylish.
Taking the wider view of the tech industry, it's unclear whether the iPhone 4S is enough to keep Apple on top for another whole year. But forget navel-gazing -- right now we reckon this is the best smart phone out there.
It's a cracking little gadget and it's loads of fun to use, offering more apps, games and multimedia than you can shake a stick at. It's not nearly as striking as its predecessor was, but if you're on the hunt for a powerful, easy to use mobile, this should be your first choice.