I have a button on my desktop that runs compiz-start if compiz is off and metacity --replace if compiz is off. I'm having fun playing wtih this thing except one annoying feature is when I switch from metacity to compiz all existing windows are bumped up by one titlebar's worth. this means that all windows that are maximized or at the top will have their titlebars undder the gnome-panel.
An easy start+down with the place plugin moves the window down, else an alt drag will also do. But is there any way to prevent compiz from putting titilebars under the gnome-panel at the top of the screen? -- thing.