I too was skeptical of the new design, especially after just getting burned on a Steyr M40-A1. Awesome gun, but has widespread reliability issues with FTE's. So instead of taking 2 or 3 months and sending the gun back to the factory a few times to get it to work the way it is supposed to work out of the box, I dumped it and looked to the M&P and the XD. I had an XD when it was the HS2000 and loved it. Still love them, and I plan to get another one some day.
But the M&P just felt like a great gun, got rave reviews, so I gave it a try.
Marvelous gun. Very accurate, mine is totally reliable so far, and it is very easy to take down.
Drop the mag, clear the gun, rotate the take-down lever downward(just like the XD) and slide the slide forward as you press the trigger. Takes 5 seconds, literally.
The *only* complaints I have about the M&P:
1) Stupid magazine rattle is annoying.
2) No .45ACP version yet!
;-)