Dragging a window around the screen with the latest metacity is unacceptably slow; it moves the window in jerks about once per second. Old versions of metacity moved the window smoothly, I guess about 20 times per second. CPU usage goes to 100% while this is happening. I'm guessing that this is due to the alpha-blended composite-manager eye-candy? I suspect that that needs to be turned off on machines where it is not hardware accelerated by the graphics card. Similarly, doing a hide-all-windows on desktop followed by a show-all-windows is extremely slow, about 1 second per window. This is with metacity-2.21.5-2.fc9.
You can turn off the compositor with gconf-editor by going to apps/metacity/general/compositing_manager and unsetting the checkbox. I don't believe this is turned on by default, so it may have picked up an old setting on your system.
Thanks, that works. I'll resolve this as Not-a-bug. But I don't remember turning this on via gconf-editor (it's not like I normally ever run gconf-editor), so I'm not quite sure how it got turned on.