John...be aware that S&W is downplaying the mag drop issue significantly. As they have with the internal lock jams on their revolvers. We have no way of knowing the actual extent of the problems from a numbers or percentage basis, but there have been enough problems reported just here in this forum (which no doubt represents a very small portion of actual M&P users) to indicate that the problem is not insignificant. And popping in a new mag catch isn't necessarily a lasting fix.
With my M&P 40 Compact MP "Nxxxx" I have been given five different mag catches and told each time that all I needed was a new, revised mag catch and that everything would be fine. My frame was examined by them and deemed to be fine. After the fifth catch replacement they decided to replace my frame after all. Well... things were fine with each new mag catch - for a time - sometimes a few hundred rounds, once after just 50 rounds or so. And then the problems re-occurred.
So, I don't mean to discourage you, but I honestly think the mag catch problems will not be going away for good until several different aspects of the mag catch are modified, re-engineered... as for what those modifications would be... they're detailed elsewhere on this forum.
I would want to experience 1500 to 2000 rounds without a mag drop and also without finding noteworthy wear on the mag catch engagement surface before beginning to have the kind of confidence that I need to have before trusting a firearm for carry use. THe M&P is a wonderful gun in nearly every regard except mag catch sensitivity. And unfortunately, mag catch sensitivity can easily stop the gun in it's tracks.