I am a big fan of the Beryl window manager for Linux and normally I use it on my Laptop which runs Fedora Core 6.  Beryl has a serious problem running Swing based GUIs because of a compatibility issue with some awt libraries in the JRE.  There is a bug open here that talks about it in detail and it appears as if Sun may not be too happy creating special code for each window manager that doesn’t do re-parenting, so they have currently only fixed it for Compiz.  In the comments for the bug, someone posted a link to a quick how-to on the Beryl wiki that extends the patch Sun has implemented for Compiz on which Beryl is based.  Anyway, I know a lot of Java folks switch back and forth from Beryl to Metacity so with a little work as outlined in this wiki page you should be in able to work in Beryl non-stop.

Update: This how to only works for JDK 1.6 AFAIK….