how to replace gnome-shell with a different window manager?

[James Ralston]

I've spent a few hours playing around with gnome-shell under F15 Alpha
on my laptop, and I'm throwing in the towel.  It's an interesting
idea, and hopefully it will continue to improve, but it's clearly not
for me.

How to I tell GNOME (or, more specifically, gnome-session) to run
/usr/bin/sawfish as my window manager, instead of
/usr/bin/gnome-shell?

(Note that sawfish doesn't support the --replace option, so that won't
work.)

Thanks...