Gnome is moving ahead making great progress. Every successive release gets better. A new addition to Gnome is a build in shell supporting compositing. Install it in Ubuntu with:
sudo apt-get install gnome-shell
Then implement it the same way you implement compiz:
sudo gnome-shell --replace
You may want to have the fusion-icon open in the system tray to conveniently switch back to compiz if you want. Install the fusion icon with:
sudo apt-get install fusion-icon
Gnome shell is interesting. Clearly there are three ways to use Gnome at the moment; default, gnome-shell, and Compiz. The default shell is good for a server environment, but with the stability of the alternate shells there is no reason not to use Compiz or the now available Gnome shell.