Just got my Win 7 Ultimate RC 64-bit installed about 2 hours ago. Got to use it properly about an hour ago. So far I have been completely satisfied.
Me likes what?
After the installation I got on to the Internet right away without having to battle hordes of bloodthirsty drivers all hellbent on not working. It didn't require any drivers at all. The graphics card was another thing. While I downloaded Nvidia's Win 7 drivers that supported my card as well which is odd (laptop, and Nvidia isn't known for making drivers for 'em) they didn't work. It gave some sort of error about a supported display adapter not being found but then in came the heroic rescuer - Windows Update which provides the latest WHQL accepted drivers for Windows 7. Guess what? My graphics card being among them and now this runs peachy.
While a bit weird at first the looks of this OS is awesome, when modified to your own liking.
..And well, just about anything else. But this isn't the most perfect OS.
Without modification I think the stacking icons on the taskbar are horrible and should be buried 6 feet under in a locked trunk made out of titanium and the key should be destroyed in a furnace. Gladly you can turn it off.

And and.. what else is there..
Well, the icons on the taskbar are huge, and when something is minimized into the tray it's pretty hard to dig it up from there - again - this is totally adjustable so it can't be held against it that much.
About performance, this clean install takes me about 1 minute to be all set to go at the time being compared to my Vista's 2 minutes so yay for this. Also, much lighter than Vista.
So far I've only tested out World of Warcraft from games. I didn't notice much of an FPS-boost in it, but tomorrow I'll be checking out at least GTA IV, Team Fortress 2 (I'll call it a day if TF2 manages to start up faster than in Vista where it took about 1min+) and Half Life 2.
All in all, I am - at the time being - very happy that I decided to wipe my HDD clean and put this in. Hope this gives you some directions if you are considering this OS.
