Here is my belated reply to this thread.
My M&P45 broke its trigger pin and became inoperable after about 3500-4000ish rounds.
I've had problems with my M&P9.
First, it would completely fail to extract a case one time out of every 200-400 rounds. This happened with several types of ammo, including Ranger. It seems that the 9mm uses the same extractor as the original .40. An Apex extractor completely eliminated this issue and I have not had one in like 2K-3K rounds.
I have also had the slide release on the left side break after about 5000ish rounds:
But the issue that really bothers me is that I've had about 4 or 5 instances where the rounds in the magazine got lodged together and the mag would not feed. This has happened with a different magazine each time and happened despite the fact that I have upgraded followers and installed ISMI extra powered springs.
Below is a picture of it:
I suspect that it something was not done right with the redesign of the magazine for 9mm that makes it vulnerable to this.
When you look at the number of occurances that I have had divided by the number of rounds through the gun, it only translates into one instance per 1200-1500 rounds through the gun. But I have not had this happen with any other gun, so it bothers me.