Some of the tips may apply to only Gnome 3.0 and 3.2, be aware of the switch from gconf to gsettings (or whatever).
How to switch modal dialogs from attached to decorated+movable in Gnome 3.2
gsettings set org.gnome.shell.overrides attach-modal-dialogs false (or use
How to include the 2nd monitor in workspace switching (
gsettings set org.gnome.shell.overrides workspaces-only-on-primary false (or use
How to reduce the time after which Alt-Tab shows the window list (watch out for the comment about
To give workspaces names: