I just upgraded my mouse from an M$ explorer to a Logitech MX510 and I love it to pieces, but the whole "USB or PS/2 port?" discussion came up and I learned a few things. First up, it is generally better to go thru your PS/2 port over a USB one. Your PS/2 port can be "overclocked" to 200 samples thru XP so it will be about the same speed as the USB tweaked, but you don't use your PS/2 port for anything else. (USB has to use some system resources) USB port "overclocking" is generally a losing proposition....very little noticeable gain but lots of opportunities to hose your rig. I'm not knocking the utility, I just thought I'd share my findings over the last few weeks on the subject. I changed from USB to PS/2 with my MX510 and it runs great. :)

Too bad you were proved wrong in the thread.. Just test it with a drawing program, the higher the bus rate, the easier it is to draw a circle for example. The logic is pretty simple too... Eventhough your monitor doesn't draw every position of your mouse cursor, programs get all positional data. More data, more precise movement.

PS/2 port highest samplerate is 200hz. USB can reach 500hz and even 1000hz easily! MX510 max rate is 450hz. anyway as a CSer i cant play without that tool. bottom line: USB > PS/2