before the X10 i had the X1 which was Windows Mobile 6.1 i think, it was really not that good but i didnt mind the OS that much and wanted to move to the HD2 on renewal as it looked a far better phone, this was also before the market for android exploded to where it is now. the X10 was announced and caught my attention so i went for that upon its release. having had various phones, from Windows Mobile, webOS, Android, i have to say i prefer the customisation available with an Android handset.
if going to a Windows phone i would highly suggest nothing less than the latest Windows 7 but from my experience i wouldnt rate Windows Mobile highly at all, i'm pretty sure the latest release is far better than the one i had so without trying it i cannot comment.
but the HD2 is not on the latest software, infact the phone is what, 2 years old now?
why go backward in technology?
i had read a lot about the HD2 when i wanted one but at the time Windows 6.5 wasnt really getting any good reviews although it was stated that the HTC Sense was pretty decent and hid the WM pretty well.
i guess the HD2 isnt a bad phone but then its also very out of date now.
i used to love my Sony Ericsson K750i but i would never go backwards in technology....