I spent today playing with Beryl and getting it running on Debian Etch. Beryl is a fork from Compiz and similar to XGL, and if you do not know what is is, have a look on google video or wikipedia. It is visually stunning, and while not completely stable I have not had any problems with it so long as I kept the blur and focustrail plugins turned off.
Setting it up was actually very easy. The Beryl wiki has a nice Debian install page, but to sum it up I had to add a new apt sources entry, install a few packages, edit my xorg config file, restart X and then just run it!
This is the kind of thing that will make every windows user say “What are you running? Where can I get that?”
If you are running linux I would definitely suggest you install it and give it a go. It runs as a window manager, and can be simply run manually so that you don’t have to have it on all the time (it is so new I would not call it stable, but it seems pretty reliable to me).
The transparency of a playing movie is incredible, not to mention all the other wonderful effects.