I upgraded my Edgy Eft box to Feisty Fawn today at work (my home machine is more, um, sensitive and will come later). Had a few problems. When Gnome first loaded up and I started firefox and thunderbird, everything froze. I did the magic reboot and started searching google on my other machine. Nobody has a good answer, but I have only seen it one more time, and it passed without me having to reboot.
Another issue is that apache wouldn't start because of the PythonPath directive in my MoinMoin wiki setup. I did some aptituding and it got fixed. I think I did: aptitude update, aptitude upgrade, aptitude dist-upgrade, aptitude install python-moinmoin, and aptitude install libapache2-mod-python. I think a missing mod-python was the final culprit. Don't know why that was removed during the upgrade.
Then I had problems getting the ever important Beryl to run. First I tried the new System->Preferences->Desktop Effects, but that started Compiz with none of my keyboard shortcuts and stuff that I'd set up with Beryl before. I undid that and ran beryl-manager from a command-line like I've been doing and it started, but I had no window borders (or decorations or whatever they're called). I found an Ubuntu forum thread that helped, but I went with the recommendation in this blog entry in the end.
Not only did I get window borders back, but everything is a whole lot snappier than it was with Beryl before. I'll take it.