i have 2x hd 7750 in my pc, and i i'd lie to use them booth for gaming like under windows.
i have tried modding the atiogl.xml file in /etc/ati/, but adding games to it with the "<CrossFireCaps>0x00000100</CrossFireCaps>"
serious sam 3 just ended up with worse performance(and even to xserver crashes for tf2/css). i dont know who's job it is to make games work in crossfire,
but it would be cool if it would be taken into account on linux aswell.