I have full 64 system. My specs are
HP Pavilion Elite - m9275.pt with iAtkos S3 10.6.3 with update to 10.6.4 - Core 2 Quad 2.83 GHz and GeForce GT 220.

Install went great with no extra customization. I had to alter com.apple.boot.plist with GraphicsEnabler to "Yes" (not "YES") and everything just works. Only problem I have is the famous Sleep issue. If I put my system to sleep fan speeds up on my GT 220 and I have to force shut down my system with 5+ secs on my power button. But beside that everything is working great with dual monitors (HDMI does not work - it freezes my system). If any one has any idea how to get sleep to work, please tell.

greetings from my Mac pro 3,1 HP Pavilion