I just finished with the M&P armorers course today that was hosted by the local Sheriff's Office. I've been carrying a Glock at work, and have almost no experience with the M&P. After this class, I'd have to say that the M&P seems like a great service weapon. Many of the parts resembled the internals from the Glock - especially the striker and striker channel. In all, it is a fairly easy weapon to work on. Whats nice is many of the parts never need to be completely disassembled to be cleaned like on the Glock. We were actually dicouraged from completely disassembling the weapon for annual cleaning and evaluation.
The class was put on by Mark Dix, and he was an excellent instructor.
He had examples of everything, including the frame mounted 1911 style safeties, which I think like now after working with one.
I actually only have two complaints. My biggest would have to be the firing pin safety/plunger. The only way to get it out for replacement or cleaning is to remove the rear sight. Granted, this probably wouldn't have to be done very often - if ever, but it's still a major pain to do.
The other complaint would be the use of roll pins.
I'd recommend this class to anyone thinking about going. The materials are easy to understand - especially for non-mechanical types like me, and the instruction is top notch.