just got the desire on another contract....
I'm still getting used to it, but both got its pros and cons...

i'd type on the N900 any time..
I prefer N900's screen, but hate the scratches - it gets fu**ed even if i use it with extra care.....
the minimise and close button helps a lot on maemo... you have to press back on the desire (unless there is a way out)....
camera on the desire is a bit sharp edged, need to be careful when keeping it on a surface....

market is waaay better than maemo. i kept scrolling own until i gave up...
i dont know whether half the market is useless like the N900's one....

battery life.. hmmmmmmm much better than n900....