If you can shoot well with the stock sights, I'd leave them on because they won't rust like some of the other sights, even my Heine Slant Pro can rust after a day of CC in heat and humidity ... which is why I dry them off after each day's use and then rub them down with a silicone cloth before I leave the house.
Regarding the extended slide stop, I've also had a few issues with my high-thumb grip, either going to slide lock with rounds in the magazine or some other variant. I have never had any problems releasing the slide with the stock slide stop, so that's just one more OEM part that I leave in place.
Regarding how smooth the trigger is, or how it breaks, I'm not sensitive enough to even really notice, but I will say that after a few hundred rounds, my past Glocks have all felt very good when I squeeze the trigger ... especially when they ALWAYS go 'bang'. Some of my other guns didn't always go 'bang'. A problem in my book ... :-)