I downloaded and tried Windows 8 for awhile, on one of my extra Quad Core machines. I ran fine, and there was no issues with the actual download and install except that it took a LONG time to download and install.
I stopped trying it because I didn't like it. I didn't like the way it looked, and they way the user interface behaved. It was a confusing operating system, that feels like you are going in circles trying to find anything. Windows XP and Windows 7 in my opinion, are THE best microsoft has come up with so far. I really don't see ANY reason to bring about Windows 8. I think MS should stop trying to come up with something new, and just work on perfecting Windows 7.