I started comparing it to different pistols I tend to like, (while impatiently waiting for my slide to come) and they really did some research when designing it, I have to give credit.
I love the M&P full size feel, the front grip angle and trigger guard inside shape is nearly identical, but they gave the little finger groove at the top of the trigger guard and a lip on the front bottom of the guard for better control where the M&P is slick. The grip is not configurable which has been popular on several pistols, but is obviously designed to work well with a good variety of hands except the extreme ends of size. The grip has a wider heel portion, while the top is just slightly narrower, that allows smaller hands that ride higher to grip it properly, but larger hands still feel filled and supported with the lower heel taking up room. Width is similar to Sigs P229 series with a fairly consistent thick grip, where the M&P uses swells and larger backstraps to take up room.`
The back of the grip is nearly identical to the Walther P99, with just a slight moderation of curves.
So looks like front of grip, trigger guard and trigger is M&P derived, the back strap is Walther, the slide is CZ P10 . sig320 influenced in shape and all on Glock compatible parts.
Not that any of it is at all crucial, spend enough time shooting anything it becomes normal, but it is nice to have similar grips among various pistols if you have several different ones. It's easier to get a consistent presentation and sight picture if you don't have to consciously adjust your wrist angle.
I have handled the Polymer 80 pistols, and have not been that impressed, the slide was decent and trigger fairly nice, the one I played with had a P80 flat trigger, it was a little better than the OEM Glock triggers I have experienced, the grip and frame were kind of meh, seems to me the main draw was having a "homemade" Glock before the .gov ruined that.
I'll be curious about the trigger, I am one of those weird people who didn't mind the M&P hinged trigger, mainly because mine have a decent break. I do tend to like flat or at least flatter triggers, and did pick up a P80 flat trigger and bar in case I want to swap it, being ridiculously cheap to try at 20 bucks. Try that with a S&W.