Just saw an M&P ad in a magazine over the weekend. The headline(as I remember it):
"The break in period ends when you pick it up"
So I would just go out and enjoy!
If the M&P passed the extensive torture tests I read about by LEOs, then I would hope it it could be fired out of the box at the range without any major issues.
But it never hurts to properly clean and lube it beforehand.