I bought an M&P Pro Series with the 4.25" barrel in July 2011. I shoot it every two weeks and it is very accurate. If yours has that infamous M&P gritty trigger pre-travel, I highly recommend installing the Apex Tactical USB (Ultimate Safety Block). This little gem will completely remove all of the sandy, gritty feel and will give you a nice smooth trigger.
I have this item in all three of my M&P's.