HTC has a history with aluminum unibody designs and we've always been fond of them - the combination of metal and glass has an unsurpassed premium feel.
The HTC One is similar in shape to the Butterfly (just slightly more compact) and uses a similar design language, though there have been some refinements.
The change in size is due to the screen contracting a bit to 4.7", but it's still a 1080p Super LCD3 unit. The change in size, of course, bumped up the pixel density, but we'll talk about that later.
Things on the front have been moved around a bit. The face of the One is split into three - the middle section is the Gorilla Glass 2 covered screen, which is flanked by aluminum on both sides. The strips of aluminum house the stereo speakers with BoomSound tech. HTC claims they can put out sound at 93dB.
Just below the screen, on the glass are two capacitive keys - Back and Home. There are no Menu or App switcher keys. Switching between apps is done by double pressing the Home key, while the function of the Menu key is handled by a gesture throughout Sense 5. From the settings you can set the phone to accept a long press on the Back key as "Menu".
Above the screen is the front-facing camera, plus the ambient light and proximity sensors. The speaker takes the role of an earpiece during calls.
The front-facing camera on the HTC One is almost the same as the one on the Butterfly - it has a 2.1MP sensor with an 88° lens and can shoot 1080p video with HDR mode.
The HTC One uses microSIM cards, which go in a tray on the left side of the phone. As usual, you need a SIM ejector tool to open the tray. The right side of the phone houses the volume rocker, which is big and wide, just like the one on the Butterfly.
The microUSB port and the mouthpiece are at the bottom. The USB port is MHL-enabled, so you can use it for HD TV-Out and for USB Host functionality. The mouthpiece microphone works in conjunction with a noise cancelling mic at the back of the phone. Besides its usual noise cancelling duties, the second mic keeps track of how loud the ambient noise is and the phone will boost the sound from the mouthpiece to make sure the other side hears you loud and clear.
The top of the phone features the 3.5mm audio jack and the Power/Lock key. That key has a surprising talent - it's also an IR emitter hiding in plain sight. HTC has preloaded an app that helps you control TV sets and audio equipment. After years in oblivion, IR ports seem to be making a comeback though they are no longer used for data transmission.
The back of the HTC one is a big slab of aluminum that's divided into three parts by thin plastic lines. The noise cancelling mic is placed on the upper line, but the star of the show and arguably the biggest innovation on the HTC One is the camera.
It features a 28° wide-angle lens with F/2.0 aperture and an optically stabilized 4MP sensor with ultra-pixels. It's the most advanced camera system we've seen on a phone since PureView. Not that it's necessarily better than Nokia's tech, it's just that it involves the same high amount of innovation that's so rare to come by these days. We know 4MP sounds low, but check out the camera section of this preview for more info on why that's not necessarily a bad thing.
The HTC One features a 2,300mAh Li-Po battery that's fixed inside the metal unibody. It's non-replaceable, but it's about 300mAh bigger than the one in the HTC Butterfly and the same capacity as the battery in the Sony Xperia Z.
The HTC One is 9.3mm thick and the curved back makes it feel slimmer. It sits very well in the hand and the aluminum back both feels good to the touch and is good at hiding fingerprints. The phone weighs 143g, about the same as the Butterfly or an iPhone 4S. The weight is pleasant and gives the phone a solid feel.
The HTC One goes for a 4.7" screen, instead of 5", which is the current standard for 1080p screen phones. That makes its screen 12% smaller than the 5" models, while increasing the pixel density from 441ppi to 469ppi. The increase in sharpness is not noticeable as 441ppi is already beyond the limit of the human eye.
The 300+ ppi screens of last year's flagships are pretty close to the limit, but the update to 400+ ppi isn't about individual pixels - even though it's pretty hard to see jagged edges on them, the 400+ ppi screens just look smoother. It's a subtle difference, but it's there. The difference between 441ppi and 469ppi on the other hand is not noticeable.
But there's more to the Super LCD3 screen on the One. HTC have been putting out some excellent screens recently and this one isn't an exception. The viewing angles are great, there's no shift in colors and only a slight contrast shift at extreme angles.
The screen is laminated too, meaning the individual layers of the screen fit as closely as possible, bringing the image as close as possible to the outer surface of the glass.
We put the HTC One side by side with the Samsung Galaxy S III. The Super AMOLED wins out in terms of contrast and color saturation (those are the typical advantages of the tech), but the HTC One screen is close behind it and it's excellent for an LCD unit.
It is more reflective than the S III screen, however. It's also not the brightest screen around, but sunlight legibility is still very good.