Do not belittle the HTC ChaCha. It is actually one of the more powerful smartphones out there in terms of software integration. The ChaCha runs on the latest Android 2.3 Gingerbread OS with HTC's very own Sense user interface. According to HTC, the Sense interface (codenamed 2.1 for Messenger) is optimized for use in the landscape screen of the ChaCha.
The HTC Sense 2.1 for Messenger is quite different from the HTC Sense 2.0. It takes a leaf off Sense 3.0 by featuring the new lock screen, where you can drag an app into the circle to unlock the screen and open the app simultaneously. There are only four devices at the moment which has this new lock screen: HTC Flyer, HTC Sensation, HTC ChaCha and HTC Salsa. For detailed description on how the new lock screen works and looks different from HTC Sense 2.0, you can check here.
To accommodate the smaller 2.6-inch landscape screen, HTC tweaked the Sense interface on the ChaCha. For example, the home screen takes on a new look where three apps are arranged vertically on each side, with the clock taking the center focus and social feed widgets situated just below it. While some changes are necessary to maximize the available screen estate, some apps look unusual on the ChaCha, forcing you to switch between portrait and landscape mode.
Of course, the main highlight of the HTC ChaCha is its dedicated Facebook button. The button allows you to update your status, upload photos, "check-in" to locations, share the music titles you are listening with a single press. It is also context-aware, giving off gentle pulses of light whenever there is an opportunity to share content or updates on Facebook. The button basically eliminates the need to go through several layers of menu to accomplish the same tasks.
HTC has thoughtfully included a Facebook Chat widget on the ChaCha. On the widget itself, you can see if anyone is online and available for chat. Tap on their names and start an instant live chat.