However, the live window previews still don't work in GNOME Shell (because this feature requires Compiz).
Here is a video I've recorded with DockBarX running in AWN (and live window previews activated of course):
Install DockBarX in Ubuntu
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install dockbarx dockbarx-themes-extra
To install the AWN applet, use the following command:
sudo apt-get install awn-applet-dockbarx
Once installed, look for "DockBarX Preference" in the menu / dash to configure how DockBarX or DockX looks and behaves.
To launch DockBarX in the stand-alone mode, press ALT + F2 and type: "dockx". If you use Gnome2 panel or Avant Window Navigator, DockBarX should show up in the applet list so add it like with any other applet.
If you're not using Ubuntu, download DockBarX via Gnome-Look.