Here's a group shot of the devices showcasing HTC's UI milestones.
HTC started toying with UI customization -- dubbed TouchFlo -- on its first Windows Mobile-powered Touch in 2007. This model here is the Touch Dual, which is a slider variant of the aforementioned device with almost identical specs. You can see that the clock widget was already a big deal from day one, albeit in a different style.
The idea of TouchFlo was to make Windows Mobile devices finger-friendly, as opposed to having to use a stylus for the tiny buttons. By swiping your thumb up from the bottom of the screen, you would activate a 3D cube-like UI, though there were only three panels: productivity apps, entertainment and contacts. Given the relatively low-power specs, the smooth animation is rather impressive even today, but the Windows Mobile UI itself lacks such slickness.
The Touch Dual has a spring-loaded numeric keypad, which is a rare feature these days.
TouchFlo 3D was really what made HTC famous. The Touch Diamond, launched in May 2008, was the first device to feature what would later become the company's two iconic UI elements: flip clock and weather animation. The deep and slick UI integration made HTC stand out from the crowd, and it pretty much pioneered the idea of the carousel-style home screen.
The seller who sold this second-hand Touch Diamond to Richard Lai said that when this phone just launched in 2008, the local shops imported them from Taiwan for HK$6,000 (about US$770) each, paid HK$120 (US$16) to flash the Chinese ROM, and then sold them for just under HKD$7,000 (US$900) each. The man added that many people bought this device just to watch "high quality" stream of the World Cup on this "large" 2.8-inch display.
The gorgeous back of the Touch Diamond (and hence the name).
The HTC Hero, launched in June 2009, was the Android device that brought Sense UI to life. The flip clock plus weather widget preserved HTC's design language in TouchFlo 3D, and it would stay that way until Sense 5.0. Likewise for many of the preloaded icons.
To take advantage of the capacitive touchscreen (instead of its yucky resistive predecessor), HTC also developed its own virtual keyboard, which was "probably the best touchscreen typing experience we've ever felt" at the time. Oh, and the original Sense supported Flash video playback out of the box, which was a big deal back then.
Sense 2.0 is basically its predecessor enhanced with multi-touch capability, Friend Stream social media aggregator, Leap home screen toggler (to take advantage of the pinch-to-zoom feature), customizable "scenes" and new widgets. This was launched on top of Android 2.1 with the Desire plus the Legend in 2010, and it was offered as a free update for the Hero. The Desire would later receive a Sense 2.1 update with Android 2.2, as featured on our own device here.
While the Desire S was announced with Sense 2.1 on Android 2.3 in February 2011, our own device has already been updated with Sense 3.0 on Android 2.3.5. This would be the last Sense to feature the three-button dock bar (with app tray button, phone button and personalization button) on the home screen.
The most notable feature of Sense 3.0 was the activation ring that you drag up to unlock the phone, and you could also pull one of the four app shortcuts into the ring to directly launch the app. Other then-new goodies included customizable lock screens, trace keyboard, 3D transition effects between home screens (up to seven of them) and the recently-canned HTC Watch video streaming service.
Sense 3.0 was actually launched with the HTC Sensation in April 2011. Almost half a year later, HTC launched the Beats Audio-enabled Sensation XE, which gave Peter Chou an opportunity to lay some tracks with Dr. Dre. Alas, this unlikely friendship ended in late 2013. Our Sensation XE would later receive the Sense 3.6 update along with Android 4.0.
The Desire almost got left out of the Sense 3.0 update due to limited internal memory, but eventually, HTC would solve this problem by taking away some preloaded apps.
While the lock screen hasn't changed much in Sense 4.0, HTC has finally swapped the flip clock's font with something thinner and more elegant, and it's no longer sat on top of a semi-transparent grey tile. On the same note, Sense 4.0 was just lighter overall in terms of design language.
The old three-button dock bar on the home screen is replaced by a tray that hosts four app shortcuts, as well as the usual app tray button in the middle. This feature was also offered in Sense 3.6. Other tweaks include horizontal scroll instead of vertical scroll in the app tray, card-style task switcher, revamped system apps and Beats Audio support for all apps.
HTC took a leap of faith with a brand new design language in Sense 5. It's clean, very minimalistic and features many handy goodies like BlinkFeed, Sense TV, Zoe camera and Video Highlights editing tool on the HTC One (2013). Sense 5.5, which was launched with the One Max and later offered to other recent devices, enhanced the gallery app's UI, added more options (including a toggle switch) for BlinkFeed, added a cool visualizer in the music app and increased the flexibility of the video editing tool.
Sense 6 is similar to Sense 5.5 in many ways, with the main difference being the new and more intuitive layout in the camera app (along with new features that take advantage of the Duo Camera), as well as breaking Zoe out as a separate app, exclusive Fitbit integration (which can use either the phone's pedometer or your Fitbit device), a more colorful BlinkFeed and Motion Launch gestures while phone is on standby.