I shot the 5" 9mm pro this year in competition. love everything about it except the trigger, which i've learned to like. :) I started many years and many rounds ago with a sig 226. its the closest striker gun i've got to its feel in the hand. I also find the stock sights very usable on the regular models. the mag bases are another story. i found out you could switch the long nose stock ones with the short nose compact ones. this gets their feel more like everybody elses.
I liked the m&p so much i eventually got a 4" pro in 9mm for home/comp backup/cc and i primarily carry a 9mm compact with stock trigger and crimson grip.
I've never tried/felt an apex trigger but from what i read, the pro triggers are close/= to them. there is a definite difference between stock standard and stock pro. my only complaint with them is they all feel springy. I had an xdm before this and it absolutely had the best factory trigger i've ever felt. i wanted to keep the xdm but they just didn't feel as good ad the m&p in the hand.
on the slide drop thing. i was told its actually because the slide is driven slightly backwards on a forceful mag seat. this disengages the slide stop and forward she goes. i didn't like this at first but i have learned to like it for competitions and none of mine have failed to grab a round yet.