Here is an xorg.conf for a Gentoo guest running in VMWare Fusion on MacOS 10.6 (Snow Leopard). It’s surprisingly simple to set up X when the hardware is fake 😉 Gentoo runs great on a Macbook Pro 13″. I was concerned at first about the lack of 3D acceleration, but I tried a few 3D applications and found the performance to be acceptable. Blender ran really smoothly with a simple model (once I found out that command-click is equivalent to middle click). Rotating a field of several hundred spheres in Paraview was a little slow, but still very acceptable.
I also bought a Logitech wireless mouse, and found that the middle button works just as you’d expect (paste) in Gentoo running in Fusion. I didn’t have to install the Logitech drivers in OS X.