The accuracy issues are real but they aren't as bad as some make them out to be. Last I heard Apex pinned the problem to the barrel/slide lockup and they were working on a fix. My M&P9... I don't notice it. But the issues are mainly past 25 yards and I can't remember when I last shot farther out than that.
Someone might confirm or deny this but last I heard S&W was not doing anything about the accuracy issues via warranty because it was in spec? Someone can correct me if I'm wrong there but I recall reading that over at M4carbine.
The M&P is a fantastic choice if you are looking at Polymer.