RC2 (Build 1433) is now out, at the same link as RC1 was at. Should be a better release with more support. I already have it downloaded, but won't be installing it until I can devote a separate partition for it.
At any rate, MS is supposed to allow 32-bit client licensees to convert to 64-bit licenses on a 1-for-1 basis at no charge, from what I've heard. So if you already have XP-32, you can get 64 when it ships if you need it. There is an expiration date on all release candidates; most MS demos or RC's I've seen have either 120 or 360 days.
Intel Q9450 @3.2GHz, Gigabyte GA EP45-UD3P, 4 x 2GB G.Skill @4-4-4-12
Antec P160SW case (modded), Xigmatek 750w PSU
3x 500GB (RAID-5), , OptiArc 7200S, ASUS E818A3T
Creative X-Fi XtremeGamer, Hauppauge HVR-1800, Radeon 4890