I've recently upgraded to Ubuntu 12.04 and things went surprisingly well so far as I can tell. The one big issue I have right now is that I can't get the launcher to hide or dodge windows. I've gone into Appearance / Behavior and set the "hide launcher" to ON, but I'm getting no launcher hiding love. Is there something I might be missing?
What worked for me was installing compizconfig-settings-manager, checking off "enable Unity plugin" and setting the Hide Launcher mode--Unity ran fine before this, just didn't dock.