The guys at OpenGL and on #beryl-dev were very helpful in increasing my understanding of how Beryl works. There hasn't been a lot of testing done of 3D desktops over remote display, and I volunteered to do what I could to test and improve this type of deployment.
The first step is to build a baseline of how it works now, and then monitor as patches and changes are made. It's my understanding that for a crisp 3D desktop one wants to have around 100 frames per second from the Beryl Benchmark plugin. When you drop below that it works, but feels sluggish.
My baseline is to log into GNOME, start beryl, and have Evolution and one gnome-terminal window open. Based on that benchmark, Beryl runs well for all of the 16 bit color resolutions, and will support 24 bit color in 1024x768. 1024x768 is the standard for 99% of 'Office Workers'. Once you go higher than 1024 in 24 bit color, it begins to slow. The highest I tested was 24 bit color, 1680x1050 which works, but is a bit too slow to deploy. Window movement is not crisp, and applications take a while to render and scroll.
I'll put the Nvidia card back in again after Christmas and perform the same test. Thanks to everyone that is helping me understand how it all works. It's certainly something that could be deployed.
(Benchmarks below, go to my blog if the chart does not appear).