Overall using CAT5 is a lot easier, just don't make the mistake of thinking that it's ethernet. CAT5 just provides the wires, the signaling is proprietary and would probably fry an ethernet port if you plugged one in. I suggest using different color cables specifically for the KVM connections.
That may be true for the solution you know but certainly it is not true for many solutions out there. Look for "KVM over IP".
As a quick example, see this page:
http://www.lindy-usa.com/kvm/extenders-listed-by-features/kvm-over-ip/
You can even control equipment over the Internet.