A quick impression.
Well I'm up and running on Windows 7 thanks to the people at PC Wank, and up to now I'm very impressed with it, boots up in 45 secs and shuts down in 15. Ok, there were security patches to apply after installation but that's Micro$oft for you. The layout is impressive and easy to navigate (Anything is better than Vista). WMP 12 has been improved with it's layout and has it's own codecs but it doesn't play flv files. It's a hell of a lot faster than Vi$ta and not as many "are you sure you want to run this" security prompts. No crashes (Yet). I'm running Firefox 3.5.3 without any problems and apparently Mozilla will be releasing a 3.6 beta on the 21st with improvements for Windows 7.
Installation took about 45mins on a clean install.