memfungsikan alt tab di gnome session fallback di ubuntu 12.04

sudo apt-get install gnome-shell
sudo apt-get install gnome-session-fallback

Install first CCSM with this command from the terminal:
sudo apt-get install compizconfig-settings-manager compiz-plugins

Start now CCSM with this command:
ccsm


In the left pane of the window, click Window Management, then in the right side of the window, check on "Application Switcher":

You have now enabled the ALT-TAB behavior!

A bug has been reported to Launchpad on this issue. Until it's resolved, install Compiz Config Settings Manager, then use the "Scale" settings there to set ALT-TAB as you want it. Works nicely, actually.