I have the M&P 9c and the full size M&P 45. The compacts had a few issues with a few of the earlier models. The issues were mag drops, FTF's, and premature slide locking. From what I've heard though, S&W has excellent customer service and everybody's issues have been fixed with shipping paid by S&W and the later models seems to have most of the issues worked out.
My 9c has approx 600 rounds through it so far with no problems at all. The trigger was a little stiff and the slide lock was a little hard to release but they're both starting to break in nicely. Mine is definitely a keeper and will soon become part of my everyday apparel.
My M&P 45 also has 600 rounds with no issues. I can even hit paper at 100 yards with it.
Not to mention that they're great looking pistols and "Made in America" to boot..!