I've made my own timedemo in RTCW MP at (BS) server and tested it on both Linux and WinXP with exactly the same settings.
RH FC1: 150FPS
Radeon9800 flashed to R9800Pro, AthlonXP1700@2145Mhz(11x195).
And I think that the textures are nicer and more sharp in Linux than in WinXP. Drivers used were 3.7.0. UT2004 demo runs bad, RTCW ET runs good, but not nearly as good as in WinXP; with some flashing textures as well.
I will also try 3.2.8-6 drivers as it is said that they are better.