Actually, WinBox should be implemented in Java, so it would be portable to everything without a problem. I personally run a windows XP desktop, Mac OS X desktop, Mac OS X laptop, Linux desktop, and have a palm-enabled phone. The only machine I can run winbox on is the XP desktop at the office, but it would be great to run it from any of the other machines I have.
In addition to my main MT router, I also have a Cisco PIX firewall, which has a GUI written in java. This works out REALLY well, as I can use it from any desktop, not just the windows boxes.