I had same problem, but, however, in my case adjusting compiz settings didn't help a lot.
I also had ATI drivers installed. Then I noticed ATI had JUST released new ones, which are said to have much better supprot for the latest X and Unity. However, ATI released them too late, and they failed to get into Ubuntu repositories.
What I reccoment you is to uninstall the ATI driver (fglrx) Ubuntu installed for you, and get the newest one from the ATI's site: http://support.amd.com/us/gpudownload/Pages/index.aspx
In my case this provided incredible improvement of overall performance. I hope it will help you too!