Also compatibility wise, I haven't run into any problems. I liked how my printer on the WiFi network was detected correctly during OS install, and was functioning after first boot. On Windows 7, I have had bunch of problems, getting the printer work correctly on WiFi, if I choose to restart windows. Win8 doesn't show this problem. The video drivers that come with the release preview were good enough to launch most games, though I did have texture corruption in Dirt2 (in DX11 mode) until I got the latest Catalyst drivers. Creative Labs audio driver works fine for most part.
Win8 also changes how your system shuts down or restarts. By default, the OS puts the system into a sort of hibernation, so the subsequent startup can be quick, and it indeed is. However I think, the "Restart" doesn't exit the OS gracefully, and my PC gets stuck at the subsequent BIOS screen. If I turn off this optimization then the restart works fine. Hopefully this issue gets resolved by RTM. I don't think many folks are running into this though.