Glad to see someone else has it running good. I have a GT220 card and the Core i7 920 processor. I have tested with 4GB and 12GB running AMD64. I use KDE4. I have the fun kernel panic when I exit X windows. Are you using KDE or GNOME? Are you using a custom kernel? What motherboard are you using?
I'm just trying to figure out what I can since many people are reporting success while a few of us are reporting panic's.