I think it's a little unreasonable that Nexuiz can't run (above 20fps) on my Macbook with no effects, minimal particles, and gl_picmip_10. I have a really hard time believing it's completely hardware, because I can play Tremulous or Warsow at a steady 60-70fps at reasonable quality. Why is Nexuiz so bad on my computer.
Yah, I'm running a GMA950, so what.

ok you're on a macbook, so you have a fast processor (2.0ghz+?) your connection speed isn't the issue. It could be that you have too many progs running, or downloading stuff, your computer is near- out of range of the airport, so your connection is limited, or the servers you use tend to lag. just to test the latter, do a campaign like thing. those shouldn't lag.

Well gma sounds like an intel graphic card which are not know for power.. And the games or rather they engines you cited function a bit different to Nexuiz/Darkplaces.. if you know a good engine developer willing to help and invest time bring him on!!! Other then that you might try the hotfix and see if that gets more fps.. someone reported a nice improvement on an ati card, not sure how help that does on intel hardware..

Make sure you haven't got hdr, opengl-2.0 shaders or dynamic lights / shadows activated.

turning gibs to zero helped me a lot, those damn gibs are the only thing that slows down the game for me.