I ran Feisty for a few months now. Got some major problems in the beginning with my Dell D830 (and the intel 965GM videochip) but I got it up&running without any problems (including Beryl)
Today I upgraded to Gutsy Gibbon and after a 1,2GB download (yes, I have much installed) the system rebooted and seemed to work, except Compiz wasn' t working because of an error of the videocard and sound wasn't working at all.
After a quick search thru this forum I was able to get back my sound (also Intel chip) and on the Dell wiki there was a description how to enable compiz on my Dell. So, it works now and I like it a lot.
Besides that, the upgrade removed my plugins/skins from aMSN (which I had to download again) but so far as I see, that is the only thing.
I'm glad that browsing a Windows 2003 network now works without mounting using the cifs filesystem. In Feisty cifs wasn't supported with nautilus, but now it is! I also like the new compiz manager and the Xorg-fallback.
For the programmers and testers, good job y' all!