KVMs and Xkeys usb...any latency issues vs ps2?

any difference in using a USB KVM instead of regular PC mouse/keyboard cables?

You can use a USB Device instead?

I looked at this question yesterday, and failed to really understand it.

Since it's been here for so long without much of a response I figure perhaps I'm not the only one who doesn't understand the question :)

Sooooo.... what problem are you actually trying to solve?

At a guess he wants to know if the time between a key being pressed and the character making an action is longer on a USB based system or a PS2 system. Bearing in mind the signal is coming through a multiplexer...

I'd say in theory yes, but whether or not the human brain can see the extra latency is another matter. :?

PS/2 can refresh up to 200 Hz, USB mice will refresh up to 125 Hz.

The computer mouse link isn't as important as the internal mouse workings as there's no need to sample higher when only so many frames are drawn on the monitor. The calculations for movement between actual samples of the optical sensor are done ONBOARD the mouse and thus the latencies involved in the interface probably play a bigger factor than the pure refresh rate. I've always found the same mice to be quicker on USB likely due to either controller latencies or the USB->PS/2 converter latency (if there is any).

Also
PS/2 has a polling rate of 60hz

USB has a polling rate of 120hz.

This matters for mousing since the higher the freq, the more often the computer gets updated movement data. This allows for that added smootheness when playing games.