For me, it is most apparent when I try to move the optical mouse very slowly - sort of a one jerk forward, 2 jerks back sort of thing, if that makes any sense. Looks like it's trying not to move when I go slowly. So, when I move the mouse in a normal fashion, the net effect is that the pointer moves more slowly and jerkily than expected, and not as far. The faster hand movement overcomes the jerky resistance.

It's not slow in the sense of latency. It's like you're dragging a running dog by its tail, not as if you're pulling a weight with a rubber band.