I've discovered that I can have visual effects on europa identical to what I now experience with rhea and its Ubuntu installation, or I can have OpenGL functionality, but not both. Normal visual effects and OpenGL work fine together on rhea. The difference between europa and rhea is that europa has an ATI graphics card (9700Pro) while rhea has an nVidia graphics card (7600GT). Both have the respective "restricted" drivers installed. And it's the drivers that make the difference.
I was able to enable graphics effects on europa by installing xserver_xgl via Synaptic. Once installed, I restarted the X server, logged back in, and was able to select normal visual effects. And it worked. Unfortunately Google Earth hung at the splash screen, glxgears emitted warning messages, fgl_glxgears refused to run, and WorldWind-based Java projects refused to execute properly either. So, in the end, I uninstalled xerver_xgl and went back to plain old (none) visual effects. Which, frankly, is not such a big deal. This is, after all, still a beta.
But I do hope that issues with the ATI graphics and Xgl get fixed soon. Ubuntu 7.10 final is being released in 10 days.