As 73 other blogs already mentioned, you don't need XGL to run Beryl any longer if you use the beta nvidia-drivers in Portage (which are currently quite masked). This is pretty nice because the last version of XGL that worked for me was from July. I've had to mask every one since then. I got some kind of
GlxBadDrawableSomethingOrOther error every time I tried to run the new ones. I tried everything I know of (which is arguably not much) to get the newer versions to work, but nothing ever worked right. Tried every version of nvidia-drivers under the moon, recompiled my whole system once (for other reasons, but still). Nope. So this is good news. It runs at full speed too, which is also nice. A few short weeks ago, nvidia drivers + Xorg would crawl any time any special effects happened. Once again I'm amazed at how quickly the development of this project is going.
I noticed a lot of themes missing from Emerald that used to exist in Compiz/CGWD. Apparently they removed all the non-GPL themes, which is good I think. We don't want Beryl being sued out of existence by MS and/or Apple. However I don't think most of the themes there now really take advantage of the flashy transparent eye-candy that Emerald is capable of. If only I wasn't working on 12 other things and dead tired from work, I might give a theme a shot.