Shock once, than knowing exactly whats coming on repeat veiwings makes those scenes more tedious than watching action scenes play out 3-4 times imo. Now I'm not saying I want more action just making the point that it's far from "genius" because the twist isn't something like The Matrix or Inception that makes you think on it for days or question everything you know about life, existance etc. It's just ultimately a cheap gimmick which is why I think so many are pissed about it.
Personally my problem was the comedic pacing which was all over the place and general lack of respect for the parameters established previously.
I'll give an example in Nolans Batman movies he needs his cape to fly. It's unrealistic sure but they tryed to explain it somehow. Now if in The Dark Knight Rises Bruce can suddenly fly like Superman without a cape or jumping off something, just jump up off the street and fly in any direction, thats jumping the shark the character created. He's Batman so by some of your logic it shouldn't matter if his skin can reflect bullets or he's made out of jello by Bill Cosby, but I call all of that lazy writing.
It's been established Iron Man can do x because x and other can't for that same reason. So when a new guy comes in and throws that all away and says it's this way now, it's insulting to the people who watched and accpeted those first movies, it's insulting to the people that wrote those movies that way etc.