Configuring Gnome Flashback with Compiz compared to Metacity

1. Install Compiz Config Settings Manager
sudo apt-get install compizconfig-settings-manager
2. Set number of workspaces:
in Compiz Config Settings Manager go to General / General Settings / Desktop Size
set the size you want.
3. Get to know Compiz Plugins
you might find that not everything is installed by default what you want to use. in this case find out which package contains your plugin and install it.