Michael, I've done more testing and this version (2.4 and 2.3, too) works fine with Kubuntu 7.10 default radeon driver on radeon 9600. It's really playable (with GLSL and dynamic lighning disabled, but even with that it looks very good). On Kubuntu 8.04 it looks and works terrible as I've said before with 2.3, so I think it was related to driver/mesa version.
This game is great. Good work, Nexuiz Developers.