Post your specs. Also if you can try to run UT2003 on it (demo is enough). If that goes well you'll know it's not SDL but something else. UT2003 on linux goes thru SDL(and if your mouse lag with it it must be BIG problem indeed)

Have you installed your graphics drivers? Those that come normally with Linux are not for 3d or even 2d games. They are just to be there so to speak.