The Good: The HTC One M8's sumptuous aluminum body makes a beautiful background for this top-flight smartphone's brilliant 5-inch display. It runs on a powerful quad-core processor and Android KitKat, the stereo speakers deliver excellent sound, and the depth-sensing camera brings a ton of useful features. The Bad: The One M8\u2019s battery is not user-removable, making it harder to replace once the battery inevitably wears out. The phone's sealed chassis is not water-resistant, and the One M8's photos look less sharp than competitors'. The Bottom Line: Elegant style, raw power, and sophisticated features make the HTC One M8 an excellent smartphone choice for anyone but the most exacting photographer. \t \tThink of the HTC One M8 as the big-budget sequel to an Oscar-winning indie film. Last year's HTC One won rave reviews and obsessed fans, but not enough customers to keep HTC growing. This year, HTC needs a rip-roaring box-office hit with its flagship phone. \t \tIt could happen. The One M8 is undeniably the most impressive handset the company has ever minted. Like its predecessor, the M8 brings a refined and beautiful software and speedy performance, all wrapped in a lithe and eye-catching aluminum skin.The HTC One M8 must compete head-to-head against its archrival's freshest mobile machine, the , and compete it does. Aesthetically speaking, the HTC One M8 runs rings around the GS5 with its elegant and intuitive Sense interface. What's more, though the M8 may lack every bell and whistle that Samsung packs into its phones, it matches the GS5 on almost every feature that really matters, from processing speed to user interface. Only the camera and its ever-so-slightly muddy shots give me pause. \tDesign \t \tWhen the original \t hit the mobile scene last year, I was stunned by its sophisticated all-metal unibody chassis. Not only was it sturdy and comfortable to grip, but thanks to a smoothly curved back and matte finish, its polished edges elevated the handset to an unprecedented level of luxury. Frankly I'd never seen a handset look that good, and I've handled a lot of mobile phones. \t \t \tDesignwise, this certainly sets the bar high for any subsequent smartphone, let alone an HTC One follow-up. I can confirm, though, that the new HTC One M8 is one heck of a handsome device -- the sexiest smartphone I've seen all year, in fact (including the \t and the ). While HTC's latest creation is more conservatively styled than the previous One, it has a look that's just as premium. \t \tFor instance the M8's bezel (where the screen and phone edge meet) is alluringly reflective and convincingly conveys that you're holding a luxury handset. Even so, the bezel is not polished to the same eye-catching sheen as the first One was. I also found the back surface of my M8 review device, though lovingly minted in a classy brushed-metal motif, smoother than the old HTC One, which had a roughness almost like a ceramic bowl. Indeed this gray M8's slicker texture doesn't wick away moisture quite as effectively. The result is a slippery, more friendly canvas for grease than its predecessor's matte back. \t \t \tTo be clear, the One M8 comes in two additional colors (silver and gold) that don't sport the brushed-metal pattern (which HTC calls "hairline"). The fallout is that both the silver and gold versions of the M8 lack the gray model's slippery feel. And in other ways the M8 is just as beautiful as its predecessor. It uses a gorgeous all-aluminum body that flaunts a similar curved backing. The M8 also feels superbly solid, strong, and well-constructed. \t \tI admit these are minor issues and nitpicking on my part since the M8 brings important design improvements to the HTC One franchise. Notably the phone's screen is now larger -- 5 inches across (as opposed to the HTC One's 4.7-inch screen). And unlike the first One, HTC says the One M8's chassis is truly built entirely from metal. By contrast the company explained the original One's body was 70 percent aluminum, the rest being plastic. \t \tAdditionally the M8 sports a pair of powerful stereo speakers that flank the display. Also branded by HTC as BoomSound, these front-firing grilles belt out a ton of sound, at least for a mobile phone. Even better, the M8 is definitely louder and produces sound with way more presence than last year's model. It's to be expected, since HTC says it enhanced the M8's BoomSound audio system by cranking up the volume by 25 percent and improved its frequency range. Don't just take my word for it. Be sure to check out our deep dive into the HTC One \t . \t \t \tDespite the phone's larger display, the device remains roughly the same size, thickness, and weight. Tipping the scales at 5.4 ounces (154.2 grams), the M8 understandably stands a little taller yet is just slightly heavier than the older One (5.04 ounces\/142.9 grams). It's heavier than the Galaxy S5, too (5.1 ounces\/145 grams) even though the M8 lacks extra hardware such as a heart-rate monitor and fingerprint scanner.Display \t \tFrom the moment I picked up the HTC One M8, I knew its big 5-inch screen was high-quality. While it can't produce the same deep blacks and vibrant colors conjured by the OLED displays you'll find in Samsung Galaxy handsets such as the Note 3 and GS4, the M8's IPS LCD has a lot going for it. Specifically these are admirably wide viewing angles, a pleasing amount of brightness, plus rich colors. \t \tWith a full HD resolution (1,920x1,080 pixels), photos, video, and text were also crisp on the phone's screen even if it has a marginally lower pixel density than the original One (which had the same number of pixels on a smaller 4.7-inch screen). All this adds up to a display that does justice to any visual content you choose to enjoy on the M8. \t \tSome words of warning though; if you choose to view the One M8's screen in the great outdoors, I suggest you do so without polarized sunglasses. When I did this with my pair of Ray-Bans, the phone's screen in portrait orientation was dim to the point of being unreadable. Flipping the One M8 into landscape position wasn't a problem and the display was just as bright as usual under these conditions.Software and interface \t \tPremium design isn't the only ace in the One M8's hand. The handset runs Google's \t , the latest iteration from the tech giant. KitKat brings a cleaner, less cluttered layout, tighter integration with Google search, plus faster performance (especially on devices with lower specs). Layered on top of that is HTC's most recent revamp of its Sense UI, version 6 (see next section). As you'd expect from a smartphone churning such modern mobile software, the M8 has access to all of Google's bells and whistles. \t \tThis includes Gmail, Google plus social networking, the Chrome browser, and Drive file storage. The phone also taps into the company's vast universe of media content via Google's Play digital storefront. That means that books, movie rentals and purchases, games, and the more than 1 million apps hawked by third-party developers are just a finger tap away. \t \t \tYou'll find the futuristic Google Now personal notification system onboard, too, either in widget form or launched by swiping upward from the bottom of the screen. It provides insightful reminders, suggestions, and directions automatically based on your past search history, time, and location data. It's the driving force behind the Google Wear operating system for smartwatches, clothing, and other wearable tech gear.Sense reenvisioned \t \tWith every new flagship phone HTC retools its custom Sense interface and the launch of the One M8 is no different. For this latest rethink of Sense, version 6, the company says it has cleaned up the look of the Android skin to give it a freshened appearance. \t \tEssentially the overall layout of Sense 6 remains the same. You have numerous home screens to customize to your heart's content (though now five instead of the six that were in Sense 5.5) with app shortcuts and widgets. Likewise, the leftmost screen is occupied by the BlinkFeed news aggregator; thankfully HTC gives you the option to turn the service off if you don't want it. \t \t \tOne subtle tweak HTC made to Sense are colors coded to major phone features and their palette of hues coordinated with themes you select from the M8's settings menu. For instance the phone dialer and messaging functions may have a blue header while the gallery app is marked with a purple strip across the top of the screen. Settings have a special highlight hue as well, say violet. \t \tBundled with my HTC One M8 unit were three color themes: one was greenish-blue, the second warmer orange and reds, and the third skewed to electric purples and violets (my favorite). A fourth theme takes the conservative approach, consisting mostly of black and white paired with a grayscale wallpaper.BlinkFeed sees further \t \tA surprising feature HTC unveiled with the previous One last year was BlinkFeed, a magazine-like news aggregator in the vein of Flipboard. It's designed to pull in articles from a vetted pool of media outlets and websites, and then serve everything up fresh via one vertically scrolling panel. \t \tBlinkFeed is set as the leftmost home screen, though unlike the first iteration of the feature (later fixed in Sense 5.5), users can disable it if they find no use for the function. Additionally, BlinkFeed is no longer mapped to phone's home button as it was on the original One device. \t \t \tThe biggest change to BlinkFeed is that you now have the option to search for and add custom topics to the service. For example if you want to keep apprised of the latest developments in nuclear fusion, or perhaps news around aviation, BlinkFeed will do its best to return related results. Frankly it's a welcome enhancement that helps BlinkFeed approach Flipboard's level of customization. It's also worth mentioning that Samsung's similar My Magazine feature lacks this ability. \t \tHTC has also brought support for notifications from third-party apps Foursquare and Fitbit into the BlinkFeed fold. This complements existing alerts and content from social-media platforms such as Facebook, Twitter, and Google+ that were already within BlinkFeed's reach. \tA dash of gesture control \t \tNot to be outdone by the LG G2 and Motorola Moto X, the HTC One M8 also flaunts its own take on gesture-based handset commands. Similar to LG's KnockOn feature, you can wake up the M8 simply by tapping its screen twice with your finger. Provided you haven't applied PIN or pattern-swipe security (which requires a lock screen), at this point sliding your finger right launches BlinkFeed, while doing the opposite whisks you straight to the main home screen. \t \tTo fire up the camera app in a flash, just turn the M8 into a horizontal position, then hold down either end of the volume rocker (volume up or down). The idea here is to save time by not having to first press the power button to activate the display, then hunt for the camera icon. Motorola took a similar approach with its Moto X, which allows users to launch the camera with two quick twists of the wrist.