Shortcuts to move windows across multiple screens in Gnome

I've two screens next each other and I'm running Gnome (Metacity 2.22). I use Xinerama to setup resolution and position for the screens. Using OpenSuse 11.1.

I would like to use the keyboard to move windows from one screen to the other one. I found some apparently useful keys under gconf-editor:

* /apps/metacity/window_keybindings/move_to_side_n
* /apps/metacity/window_keybindings/move_to_side_e
* /apps/metacity/window_keybindings/move_to_side_w
* /apps/metacity/window_keybindings/move_to_side_s

I setup some bindings, but they seem not to work properly for all windows (for example, with Firefox or Thunderbird). Sometimes, the windows return to their original position when I press a key.

Do you have any other alternative to easily move windows across multiple screens (and possibly to tile them?). I would prefer to keep the Gnome window manager, not to switch to ratpoison or whatever else.

If your screens are on separate workspaces, you can use Shift + Ctrl + Alt and an arrow key in the specified direction you wish to move it.