The hardware spec of the device sounds incredible with its 768MB ram, and 1GHz Snapdragon processor. But at most of the time, there will be a remaining of roughly 100 to 200MB free memory left. While comparing with iPhone, I still can see the difference iPhone is being far smoother. A simple test, try pulling the home screen left and right as quick as possible could show the difference. (Take the example of fruit ninja, there are times the fruit aren't thrown up smoothly on the screen, and can feel the lag in HTC Desire HD). (However, in some other game like Asphalt HD or Need for Speed Shift, it seems fine). Apart of the occasionally lag, most of the time, such as browsing, dialing / calling, radio, typing message, downloading apps, it's ok, and fairly acceptable.
In term of playing video, The phone by default it could do hardware-decoding for the following format (3gp, .3g2, .mp4, .wmv (Windows Media Video 9), .avi (MP4 ASP and MP3), .xvid (MP4 ASP and MP3) .. for other video format, such as MKV, or RMVB, I have to use an App - Rock Player , and select 'Software Decoding' to render those video. Surely, it would be slower than hardware, but would be fine for video below HD format. It can play the HD 720p video (1280 x 720) well that was captured with its own camera. But not for other kind of video type of other encoding format that was not supported by its hardware..
HTC Sense UI offers a good compliment to the default Android 2.2 UI. (I've checked the default Android 2.2 using the Android SDK before.) Indeed, it boosts up the usage experience by its default 7 spaces launcher screen that can be rearranged easily. With the addition of widgets, ( my favourite is the HTC Clock widgets), HTC Skins, it gives a refreshing look. With the variety of feature that comes with HTC Sense, it seems to make me NOT to go for rooting the device for the moment.
However, there is only a question makes me doubt.. I haven't seen a convenient feature that allow screen capture without rooting the phone?
The screen locking security - 'Pattern locking' or some call it 'Maze Lock' comes together with HTC Sense is undeniably a nice feature. :)
IMO, Android still have plenty of room for improvement, looking at the Android changes and update is still exciting to me. We can see the highlights of the Android OS from android developer site:
Android 2.2 Froyo
Android 2.3 Gingerbread
One of my concern about smart phone device, is the on-screen keyboard that are used extensively for input. HTC it offers a nice keyboard that has 3 major switchable layout, Qwerty, Compact Qwerty, and Phone Keypad, that known as 'Touch Input' in the 'Input Method' selection. But for some reason, (this is quite personal) I find it not so comfortable to type in HTC default 'Touch Input' keyboard. Although it has a very handy feature 'write', practically you can do hand writing with it, if you enable Chinese language support, and select the 'Handwriting option'. The recognition rate for a single character works very well, however, it needs very precise writing for hand-writing a 'complete word' .
so far, I'm using the keyboard layout, of "Google Pinyin". (that support both chinese and english input). Perhaps it's the Physical Layout factor, somehow, I find it much comfortable..~