Comment 12 for bug 647437

@Berman Boris: "I'm experience same issue. Unity is _extremely_ slow. Tool tips appears after ~1-2 seconds. Clicking on any of unity shortcuts, freeze whole system for a few seconds."

Thats the same situation on most nvidia powered netbooks.
Personally I had always problems with mutter/clutter/gnome-shell on my nvidia powered netbook. Gnome-shell problems solved some months ago, always the critical issue is clutter/mutter with prop graphic drivers. I do not know what Gnome-Shell developer did to solve performance issues on prop driver but they made it work fast at least. I am anyway confused about other users with intel drivers having no issues with unity although they dont have a very fast gpu. I will investigate that...