I used a TrippLite 4 port KVM for a few years. At one time, it was mixed w/ Windows, Linux, OS X, and OS 9 boxes. The newer Macs I just used a PS/2 to USB adapter. Never any problems w/ it.
Right now I'm using an Apex outlook KVM. Running Win, Linux, and OS X boxes. It has some twitches w/ the mouse once in awhile.......
Cordless mice get flying across the screen in Linux. I found it best to use a corded mouse.
Once in awhile the mouse hangs in OS X; just switch to another box, wait a sec and switch back. Make sure it is fully switched to the system before you move the mouse and it all works fine again. Usually happens when I'm switching between systems too fast.