They are supposed to have a 4.5 - 5.5 lb trigger if I recall correctly. I have heard of a lot of them being returned to the factory after it was discovered that the triggers were 7 lbs. plus. Here is a review of the Core Pro; the author returned it to get the trigger pull corrected:
Smith & Wesson M&P®9 Performance Center® Ported Pistol Review: Part 1 - Introduction, Specifications and Summary