I've used it for 6 months now with no hicups, viruses, crashes, or anything not working like I want it to do. Its also (Ultimate) much more asthetically pleasing than xp, I make use of the sidebar, I removed all of the built-in security that slowed the system down, and I can boot from my computer being totally off in around 20 seconds.
I don't get why all the people are still hating on it, but then again I have 2 gigs of ram, core 2 duo 6600, and an 8800 GTS.