With very few exceptions, I'm very pleased with the hardware design of the HTC HD2 I'm currently using. It would have been nice if HTC had integrated two better quality speakers rather than the single, rather low quality speaker. The software, Windows Mobile 6.5, on the other hand is a big disappointment even though HTC worked hard to hide the operating system by installing its Sense UI and related utility programs.
While Sense UI is largely finger friendly, whenever the owner of the device finds him/herself having to work directly with Windows Mobile, it is clear that the software was designed to work with a stylus. A human finger is just too large to manipulate on-screen buttons, sliders and the like.
Microsoft has let it be known that the HD2 would not get the update to Windows Phone 7. I guess the company must have thought that owners of high end Windows Mobile 6.5 devices would purchase a new device for the new operating system rather than just going elsewhere. I see that as a rather short sighted move.
The community over at XDA-Developers have been hard at working trying to improve Windows Mobile. I've taken advantage of several Windows Mobile 6.5 tweaks and updates found on that forum and have been pretty happy. When the phone hung four times on the same day and had to be reset each time, I decided that I should look into loading Android on the HD2. Although it clearly is a work in process, the parts of Android that have been adapted to the HD2 work quite well.
If you use a Windows Mobile 6.5 phone, I bet you'd find it worth the time to visit xda-developers.