Pros:
-Reliable. The gun has had 0 malfunctions
-Durable. There are many, many of these guns with documented round counts over 25k that have only had simple spring replacements in that time
-Easy to maintain
-Lots of aftermarket support
-17+1 capcity-Can be disassmebled without pulling the trigger (I know some folks like that)
-Reversable mag release for lefties out there
-3 interchangable backstraps
-Relatively lightweight at 24oz unloded
-S&W has great customer service
-Durable finish on melonite treated steel
-Accurate. My gun is a 2011 made model and never had the accuracy issues that have been reported in the older M&Ps
-Low Bore Axis resulting in a relatively soft shooting gun
-Easily modified to fit the shooters' preferences
-Requires very little cleaning/lubrication to run reliably
-No external safeties
-Points very naturally for most shooters
Cons:
-Poor, almost non-existant trigger reset as it comes from the factory
Chrono data:
Federal 124gr HST: 1123FPS, 347 FT/LBS Energy
Speer 124gr +p Gold Dot: 1260FPS, 436 FT/LBS Energy
Here's a video with a little shooting, a size comparison with a few other guns, a discussion of the pros and cons, and do a chronograph test with the loads above: