Hi,
I use XFree86 v4.02 (from the 'unsupported' cooker RPMS - look on
mandrakeuser.org) on my G400 and it runs pretty well. I haven't done too much
messing with it yet but 60fps in Quake 3 is pretty standard (sadly not up to
the speed of the Windows installation which manages a good 80+fps even at
higher resolutions). But all round it's pretty good - you need a kernel with
DRI support built in, and agpgart etc - I use 2.4.1-2mdk with no problems
(other than with my ethernet card which dies on APM sleep - any ideas,
anyone?)
4.0.1 doesn't work so well with the G400 - you'll tend to get horrible
system hangs unless you're root when you run the program, but check out
4.0.2. I posted my XF86Config a while back, I'll send it again if you'd like.
tom