Today I played with the HD2, comparing it to my htc TP2
The processor in the HD2 ( 1 Ghz )is noticeably much faster than the tp2 (528Mhz). HD2 is very snappy, the screen is slightly larger. While it lacks the keyboard, it has an onscreen keyboard that looks slightly larger, BUT, IMO, that kB is no replacement for the tp2's slide out hard KB. This is the major trade off as while the Processor speed makes things fly on the HD2, having to use that onscreen keyboard slows you down.
The inability of the HD2 to sit like a small laptop, requiring you to lay it flat on the table, makes watching a video less convenient.
Having that processor speed on the HD2 really makes web surfing much faster and it sports the two finger zoom, like the iphone, but zooming with the HD2 and using double tap or the slide bar on the TP2, doesn't give the HD2 an advantage, just different. Oh, the web surfing I did on the HD2 was with wifi so I had to compare with my TP2 on wifi from memory since I was not wifi connected at the time. Still, I know the HD2 was just faster than my TP2 using the web browser.