Well as you already know I installed the final version (MSDN) of windows 7 two days ago and faced a few problems.
First of all there was this funny problem with the missing driver during the installation.

Well I try to summarize the good and bad news compared with the RC
Good News

1. It is a little bit faster than the Release Candidate
2. Windows Media Player and Explorer are more stable and faster
3. Easy install of the language pack
4. Up to now I do not have the problem with unvisible windows (in the RC Version I had the strange problem that a window was no longer visible in the taskbar and ALT+TAB but after a while it came back)
5. In the Release Candidate I had also problems with memory leaks (especially Firefox) up to now I don’t have this problem
   
6. Generally the system seems to be very stable and fast

Bad News

1. The driver detection of the Release Candidate was much better (It found and downloaded every driver for my notebook but the final version did not. I had to do it manually.)
2. Sometimes the popup-preview of the taskbar does not show the image of the window (it just shows an icon)

I will update this list as soon as I have new good or bad news for the RTM.
But generally I can say that it is a very good operating system and that it is much better (faster) then vista