I enabled Autohide in both top and bottom panels, but the screen usable to windows did not update.
Filed upstream: http://bugzilla.gnome.org/show_bug.cgi?id=572573
It's fixed with metacity-2.26.0-1.fc11 http://koji.fedoraproject.org/koji/buildinfo?buildID=94402 only need to be released in the repo