Well, I fixed the wobbly mouse problem by using a razor and gently removed the teflon? feet. Then I sort of put it in the wrong place by placing part of the feet on the raised edge near the feet. I had to do it to two of the feet. That was how bad the mouse would rock.
As far as the lag goes, yeah I can reproduce what is in the video. In fact I can do even worse by doing it on a cloth surface. I think part of why the U test makes it look so bad is that the mouse is moved left and right really really quickly, to the point that the mouse is moving across the surface just way too fast for anything to track. I know for ball mice, if you jerk and move the mouse extremely fast, the cursor will even go the opposite of the direction that you want it to move. The easiest way to reproduce what I am talking about would be to take out the ball and then use your finger to flick the roller that the ball touches inside. If your eyes are quick enough, you'll see the cursor accelerate in the right direction, then shoot off in the opposite direction. Then as the roller slowly comes to a halt, the cursor will again come to a speed where the cursor again goes in the right direction. Anyway, back to why the U test makes the mouse look so bad...I believe the U test does show some delay, but at the same time part of that is because the mouse is moving across a surface way too fast. You might ask, well if it is just a simple thing of the mouse moving too fast across the surface, then I should be able to reproduce the results in the video by just flicking the mouse in one direction really fast but keeping it on the surface. This doesn't work because the laser kicks in long before you can accelerate the mouse fast enough.
I guess my point is, that I see that there maybe a lag, but I don't think it is going to bother me that much. What actually bothers me more is the rickety scroll wheel. It just doesn't feel tight enough. The main improvement I got from this mouse over my old mx700 is the weight and the charging base. It is a little lighter than my old mx700 and they fixed the contacts so that I don't have to fiddle with the mouse in its cradle so I could get the mouse to charge up.