I once had an HTC HD2, and while WM6.5 wasn't very good, the xda-developers community loves this device. I was able to try out all sorts of Android builds on this device, as well as getting WP7 sort-of working on it. Truly amazing.
My only gripe was that it was built with TMO in mind, and didn't have the right radio to talk 3G on AT&T. The battery didn't last too long either, but it was user-replaceable, so not that big of a deal.
The HD2 came out 18 months ago, and is still near par to current hardware (1GHz, WVGA, etc.). I've been testing these XDA Android releases: http://forum.xda-developers.com/showthread.php?t=957652 ; I get standby battery drain of 1% / hour, which is about the same as the original WM6.5.
My only gripe was that it was built with TMO in mind, and didn't have the right radio to talk 3G on AT&T. The battery didn't last too long either, but it was user-replaceable, so not that big of a deal.