Completely agree re: geometrically placed desktops. Gnome2's implementation was just good enough for my needs (my other required feature is the ability to 'raise/lower' a window, mapped to a key). The one reason I can't accept XFCE as a gnome2 alternative is that it seems to insist on arranging desktops linearly. I want my two dimensions, dammit.
The only thing that makes me reluctant to go back to fvwm is that configuring it was always rather unpleasant.