Re: M&P Compact
The M&P compacts are pretty soft shooting (more so than the equivalent sized Glocks).
The trouble is that they're made by S&W.
The mag dropping issue was related to using a plastic magazine catch on a metal magazine notch. It was just a poor design that caused wear to occur rapidly.
The two real significant problems they have today is their strikers (they've done like 5 versions of them, and each time, they say "it's fixed". I don't trust that it is, and only time will tell if it really is or not). The second, and more serious problem is that the 9mm and .40S&W guns unlock too fast.
Some loads will have the gun unlocking before the bullets leave the barrel, leading to heavier bullets shooting higher.
If you play with an M&P, watch how easily the slide moves back, and how fast the barrel drops down.
http://www.youtube.com/watch?v=eYhbEEv0H9U
Compare that to a Glock, and see how much more travel is required to get the barrel to drop down (watch from 2:33 on):
http://www.youtube.com/watch?v=wkHEdNx0Mk4
You should be able to feel it as you slowly work the slide in and out of lock-up, and you can start to see it in the above video examples.
M&P owners can check this themselves by shooting groups at 25y with 2 very different weight bullet (115gr and 147gr 9mm, or 155gr and 180gr .40S&W) and check to see if your POI changes by a measurable amount. Shoot that same ammo through a Glock, Sig, HK, etc...then note if the difference in POI is comparable or not.
The M&P45's seem to stay locked up longer, and aren't exhibited some of these swings in POI and accuracy that the 9mm and .40S&W guns are.
If you look around at some of the respected industry guys that were shooting M&P's one and two years ago...check to see how many still are.
All in all, they're relatively good guns for most people. They would be a second choice to Glocks for me though, currently (in 9mm or .40S&W).