The beta team is very small, but d2kx is also on the list so perhaps he will comment on how ET: Quake Wars compares under Linux and Windows.
I am going to do that if I'm allowed, but as you can guess, the Windows results will end up much faster than the Linux results (I'm having an AMD Radeon X1900 XT 512).
The Windows client is more or less open and there's no restriction to tell about it, so: I play ET: QW under Windows with all graphic settings set to High and Ultra but without AntiAliasing. Using AA is ok, but... just ok. It was necessary in Beta 1 to use AA so the trees don't look like they're from a five year old game, but they seem to force Transpareny AA or use another method since Beta 2.
I am looking forward to comparing ET: QW once again when the new fglrx driver gets released later this year. That's what I'm really interested in.
I didn't like Beta 1, too. I can't say if it was because of the Map, Beta or if I just didn't know how to play. I guess it's a bit from every of these aspects. I loved ET: QW the more I played it. I can't wait for the full game that comes with 12 very different maps!
The performance got better from Beta 1 to Beta 2, and there was another big improvement from Beta 2 to Gold.
Even if you can't play the game with high settings, I would try the demo (Windows demo is out by tomorrow) and look how it does. ET: QW really rocks, and I never played ET or Quake a lot before (but the Battlefield series, S.T.A.L.K.E.R., and most other hit shooters). The better you are, the more fun it is. At first, I never would know what I am supposed to do, after that I was wondering which class I should play etc., but if you know all the classes and how to play, ET: QW is awesome.