Oh yeah... did I mention that it has a USB hub in it? Why the hell are we still shipping PCs with 12-year-old PS/2 technology?
Easy. Because USB is not a perfect replacement for PS/2 input devices.

In short, there is no possible way on any but the fastest of current machines for a USB mouse to approximate the responsivity of a PS/2 port mouse being sampled at 200Hz (the maximum rate the port will tolerate).

Score:5, Informative