I have a GTX 260 and an 8800gt and anything that is run on the second video card is unplayable, at <10 fps. It also slows down anything on my main monitor. This may be because my second x16 PCIe slot is really an x4 slot. My windows run just fine if i only run them on the main video card however.

When the Core i7 is cheap enough, I'm gonna upgrade my system, and see if i can run more than 2 monitors without a huge fps drop.