I picked up my M&P Friday and took it out to a friends house in the country to put some rounds through it. No surprises with functionality and handled great! SHot about 100 rounds of 115 grain Winchester FMJ without a hitch. I realized the sights are a bit off though. Two things I will be changing and have both on order now. 1. Replacing the trigger with an Apex Tactical trigger. The stock trigger has that grainy, sandy feel on the uptake. Hate it! 2. Big dot sights. The factory standard sights are way off. Other than those 2 things, love it so far!
All you need to remove the sandy/gritty trigger pre-travel is the Apex USB (Ultimate Safety Block). Try that first to see if you get what you want. Believe me, it will completely eliminate that gritty trigger.
I've become used to my trigger. I had the same low and left problem, but it was me (typical - crook of finger joint on trigger instead of pad). Not to mention, after a couple of hundred rounds, I think I get a bit fatigued and start teacup-and-saucering the thing. All of my problems with my M&P9 were PEBCAK-type, and I'm resolving them slowly as I gain more experience with it.