Xonotic has had some major anti-suck taken to it since it's preview build and now they're basically at the half way mark towards it's first full release. There have been a ton of clean ups, balance and movement have been switched out (thank God), and tons of content has been added. Grab it here when you need to take a break from UT99 or just want a ridiculously fast paced game with a sky-high skill ceiling.
http://forums.xonotic.org//showthread.php?tid=2115
Also I've been snooping the cvars for this game for some time, if anyone needs any performance tweaks let me know, in particular you should punch these into the console immediately after you start it up:
cl_playerdetailreduction 5 - The higher you set this, the more the detail on characters will reduce at distances. By default this is disabled, but I can't notice anything visually different unless I REALLY look for it when set to 5, I personally keep this at 7.
cl_projectiles_sloppy 1 - You won't notice this (I've even looked for it and the only difference I saw was increased fps) basically when this is enabled there's a possibility that projectiles (rockets, etc.) will penetrate walls temporarily.
IF YOU ABSOLUTELY CAN'T PLAY WITH LOW FPS, punch these in:
cl_maxfps 0 - frame rate limit, 0 means unlimited which is what it's set to by default
cl_minfps 60 - the game will try to hold this even if it has to reduce a few things to do it
cl_minfps_fade 1337 - how quickly the detail reduces when trying to meet minfps
cl_minfps_qualitypower 1337 - power that minfps_fade uses
Also I don't know if it's just my GPU, but I notice major stutter when you enable decals on models, so you should probably keep that disabled for now as it's not very noticeable anyway.