Comment 82 for bug 12153

I just tried and <Super>+E works for me in Compiz. You can check if it's already grabbed by something else:

1) Check in the gnome keyboard shortcuts if it's assigned to anything, even if it doesn't work there disable it. (I disabled all gnome's shortcuts and re-done them in compiz.)

2) In ccsm (compiz advanced settings) go to "Advanced Search" (on the left, bottom), check only "settings value" on the left, and enter "super" (lower-case; I don't know why "Super" doesn't work for search). It'll show you on the right all settings that use it. It might be taken by something else. (I just disabled all shortcuts I don't use, to be sure.)