I just installed Win7 before I reinstalled XP... was a nice interface... installed 7gig (yea, 7 gig for windows 7, haha) in just under 10 minutes... was ready and idle after 2 reboots, and less than 10 minutes... was really quick!
I have build 7000.0.081212-1400
if you don't enter a CDKey, it'll give you 30 days till it timebombs... but all in all, can't wait to see the RTM!