I've got GTR2 running here on a 2010 Mac Mini 2,4 GHz with 4 GB RAM and Mac OS X 10.6.3. Like others, I had some trouble getting it to go under CrossOver - using 9.2.0 in this case - but when it runs, it runs fairly well.
Using DX9 and noticed FSAA doesn't seem to be working, which it does on its ISI family member rFactor 1. As in rF, in this version of CrossOverGames there is a faraway black horizontal stripy haze (moving in front of the car) on many textures which seems to have something to do with Mipmap texture bias - making it negative in the track files seems to help, as does antialiasing, which as noticed doesn't seem to work in GTR2 yet. Some tracks have this issue badly, some hardly at all, depending on the textures used.
On this machine, in a Winxp bottle, fps varies, but is generally between 22 and 42 fps, which is usable. My usb gamepad controller is recognised with no trouble. When running, the program is pretty stable and just about all the add-on mods and tracks work.
Here's part of my GTR2 config.ini (note this is on the Mini described above, screen res is 1280x1024):
CPURATING=4
SYSTEMRAM=3072
VIDEORAM=782
OBJDETAIL=3
TEXDETAIL=3
VIDEOGUID=AEB2CDD4-6E41-43EA-941C-8361CC760781
VIDEODRIVER=0
VIDEOMODE=19
VIDEOREFRESH=1
WINDOWEDMODE=1
RUNBENCHMARKS=0
FSAA=1
VSYNC=0
SHADERLEVEL=3