About all I care about from a mouse on my Powerbook is a working right click, side buttons mapped to expose, and the scroll wheel working. OS X does this fine built in, and when running a game like World of Warcraft, I can map all 5 buttons to anything.

I used a trackball for a long time with a simple 3 button arrangement. When I moved back to mice, I never got used to the back/forward functionality in web browsers, instead usually using backspace as back.

For his purposes though, it was more of a test to see if maybe the 3rd party mouse drivers were getting confused by the KVM, or if (as it seems to be the case) the kvm or converter combination was not passing through the buttons.