I bought the M&P 9 C.O.R.E. just over two months ago. I replaced the trigger with the Apex FSS kit, and it's a very nice trigger. That kit includes their new striker block, so the "grittiness" of the stock trigger goes away. Didn't shoot it much with the stock trigger, but I definitely like it better with this Apex one. You are right, though, about it taking you out of Production division in IPSC - you'll be stuck in Standard.
The Apex DCAEK (Duty/Carry Action Enhancement Kit, I think?) is supposed to make for a nice trigger too, though not quite as good as the FSS, but keeps it "legal" for Production (is my understanding anyway - correct me if I'm wrong, IPSC rule-gurus).
I don't have an optic on it (yet - who knows when or if I'll get around to that) but I see four reasons why one might want a C.O.R.E. over the regular M&P:
- ability to add an optic easily at a later time, if so desired
- nice aggressively textured backstrap inserts, so you don't have to have someone "Stipple" your grips for you at extra cost, to keep the thing from sliding out of your hands in the wet (Ended up doing my Black Badge course in the rain!) These new backstraps are reportedly not available on any other models, nor are they available separately from S&W at this time.
- Supposedly better overall trigger out of the box, if you believe S&W's promotional material. Probably not a selling point if you're just going to upgrade with Apex trigger parts, though
- This point is more subjective: I think it's possibly easier to install the Apex striker block upgrade (which comes with many of their kits, or available standalone) - in the regular M&P's, you must remove the rear sight to install this. In the C.O.R.E. series, the sight is further back, and you don't have to touch it. Instead, you remove a little plate that sits under where the red-dot optic would go. You do need a small hex wrench to do this (a 0.05" one, which is not exactly common, but not so rare as to be unobtainable) but you don't fiddle with, and then have to readjust, your rear sights. I realize that for some people, removing and re-zeroing rear sights may be easier than fiddling with small hex screws, but I prefer to leave the sights untouched, as they were pretty well zeroed from the factory
As to the reliability issue, I have well over 1000 rounds through it now, (all 124gr, mix of Sellier&Bellot and the Wolf brand commercially reloaded ammo) without one failure of any kind.
The only minor issue I've had so far is the same one that others have complained about elsewhere on the 'net - the magazines can be "tight" when fitting in that 10th round. In fact, some cynics call them 9.5 round magazines. With a Maglula loader, I never had any issues loading 10 rounds in them - just push real hard for that last one. And, as mentioned earlier in this thread, inserting a fully loaded (10 rounds in) magazine on a closed slide takes a little extra "oomph" to get it to seat properly. I've had a few instances of "pull trigger... click" after a reload, when I haven't really jammed the mag home. Solved with a "Tap, rack, bang" but annoying enough that when I did my first IPSC match with the gun, I planned my strategy carefully, and where it worked out, I'd run a stage with only 9 rounds in the mags, to ensure I didn't get caught short by a weakly-inserted mag in the heat of the moment. This whole mag thing can be easily fixed, apparently, with some careful dremel work on the follower to shorten it up a bit, but so far this hasn't been annoying enough for me to bother with trying to fix.
In the end, I am quite happy with the gun, and a friend of mine has just ordered one (also the C.O.R.E) after having tried mine.
One note: When I bought mine, they were going for $800-ish. I've now seen two places selling them for $690 or thereabouts.... So if you want the C.O.R.E., shop around a bit, you may get a deal.
Personally, I think if you can get it for under $700, it may be worth getting the C.O.R.E. S&W lists their "suggested" price as $729 (US dollars).
Anyway, that's just my $0.02 worth.. I do not in any way purport to be an expert in these matters, I just know that I like mine.
Trav