I upgraded a couple of weeks ago and am finding many issues. Most apps I use regularly have been updated..this is good. However, disk utility is unwilling to do more than beachball if I want to look for a file to burn to CD/DVD and I gave up. iPhoto has become quite sluggish. I thought it was because I was still using the older version from iLife08, but when I upgraded to the more recent version... it was worse!
About 20 minutes ago I decided that I would revert to SL until the bugs are ironed out, and right now I'm on the Ubuntu netbook, waiting for my clean install to finish, on the iMac. I'll migrate the data from my my carbon copy cloner backup, and restore all my music, docs and photographs, and beyond that, start over.
(cups ear: I hear it calling me even as we type)