I had one for a while, and a friend-shooter still runs his.
Upon taking it apart, I found a little more play than I was comfortable with, however I cannot say it didn't work well. Came upon a deal on a set of Ivey adjustable rings about the same time, so have been running them since......
Read somewhere about some guys in Australia milling the front pivot pin hole in the MOAB and replacing it with a bigger pin fit to tighter tolerances.