If you install the Nvidia beta drivers found
here then you don't need AIGLX or XGL, just install Beryl and you're off. I guess they have their own implementation of AIGLX and it works great. Only problem with the drivers is that some games get strange artifacts, you'll see them in ET. It looks like lightening or something. I've just stuck with Metacity now until these drivers are fixed and work with games normally.
Other than that, I haven't gotten Xorg 7.1's built-in AIGLX to work with the official drivers, and I don't even mess with XGL.