Just picked up an M&P 45 fs today with born on date of Jan 2013.
This new gun has a slightly gritty trigger pull. It also feels as if the final bit of the trigger pull is slightly heavy. The reset is definitely much shorter and has more of a click feel when pulling the trigger than my 4 other M&Ps that are all 4-5 years old.

The older pistols are challenging to feel the reset well. I have been focusing on that alot over the last year when I go to the range.
While this new trigger on the 45 is a little gritty, I expect it will begin to smooth out with use. My older M&Ps all have atleast 2-3000 rds shot through them and now have a buttery smooth pull.