It's pretty good. The only drawback I can see is that when you change directions (i.e. have been moving the camera towards the object, and then start moving it away) there is a slight shift in the centering of the camera. Using a regular macro it's not a huge deal, but if using extension tubes on the macro it can make a big difference in what is in the middle of the frame.
That is not a huge issue for me as I am now used to how much it moves so can adjust for it pretty quickly. Other than that it's a really nice unit and not terribly expensive.
Thanks, Al