I've been doing plenty of research on affordable IP KVMs - all the recommendations led to the Lantronix unit, and it delivers. It has funny connectors, but once you're set up it is straightforward.
I can control old-school PS/2 PC servers and trigger a clunky PS/2 KVM - all from my Macbook, key mapping and everything works fine.
I was pleasantly surprised that the unit did come standard with both a power supply and a mounting plate, even though it's wasn't mentioned anywhere.
One con: PS/2 mouse control is not good - Lantronix goes into detail in the manual explaining the reasons why, it's pretty much a technical limitation of PS/2. If possible, do buy the USB version and only use USB.
It is possible to control a USB mouse with this version of the SpiderDuo, even from a local PS/2 console mouse.