ja, nVidia sticks customized Mesa libs in your X installation. If you don't have your GL apps linking against that, they run like *gag* software OpenGL.
also, if you're just using embedded X11 drivers, you *don't* want to replace XFree86's GL libs with Mesa GL libs. The XFree86 GL libs are taken from Mesa sources, but they're tweaked a bit to use DRI acceleration--and if you overwrite them with separately-compiled Mesa libs, you don't have DRI anymore!
You do have to get one thing out of Mesa sources, though, that isn't in XFree86's GL libraries--the GLUT libraries (libglut.so.*). Or you can try freeglut (check freshmeat.net), though that was in alpha last I knew.
As for the 10FPS loss...that's not going to be because of missing DRI drivers or any of that. That's too small to be anything more than less-than-optimal drivers. If you "modeprobe NVdriver && cat /proc/nv/card0", it should tell you what AGP settings your nVidia driver is using. I've found it best to either go with AGP via the kernel's AGPGART or go no AGP at all. This can be tweaked by modifying the "NvAGP" option in XF86Config--the nVidia README in /usr/doc/NVIDIA*/ should tell you how to do that.
"/join #hackerz. See the Web. DoS interesting people."
P.S. v436 of the nVidia drivers? ummm...that's just about older than dirt by now :wink: . I'm on 1512, using XFree86 4.1.0 with kernel 2.4.7.