Working fine for me, on 64-bit, except for my Tascam USB audio interface. If you use a semi-pro or pro audio interface, check the drivers, and do yourself a favour and check out Google to see if there is negative feedback for it. In Tascam’s case, their 64-bit drivers are shocking and it seems to me the majority of users have issues with it, but they refuse to even look at it, or acknowledge it with more than “you should go back to 32-bit”.
I’m using an i7 860, and yeah, it’s working great. I’m pretty happy with it.