After updating to compiz-0.3.6-7.fc7 (and rebooting), compiz no longer honors the the /apps/gwd/use_metacity_theme gconf setting. It always uses the default compiz window decorations.
Same bug here with compiz-0.3.6-7.fc7 on two machines
This should be fixed in 8.fc7 - the metacity-devel split broke the build requires.