Sometimes when I move the mouse to the unity launcher the system freezes (sometimes I can move the mouse). I can't even CTRL+ALT+F1. How would I go about figuring out what the cause is and recover from it?
As a workaround I've disabled Unity hiding as per the description here: How can I configure Unity's launcher auto-hide behavior?
I also had system freezes with with Unity. Must have something to do with the graphics card and 3D support. I switched to Unity 2D and it is as stable as ever. Unity 2D makes use of Qt metacity in stead of compiz and is much lighter. Looks more or less the same as Unity 3D and you can alway's switch back. I would give it a try: https://wiki.ubuntu.com/Unity2D
Cheers, Maurice