Firstly, Iron Man. I think the biggest thing to come out of it was the theme of the whole thing ie testing the mettle of the man (pun intended). Seriously, give us a flawed human being, prise him out of his suit, send him into action and see what comes out. That final battle was the making of Tony Stark - oh he'll still be cocky and irritating as all hell but he'll come out of it with a deeper appreciation of his own abilities, and maybe he won't feel the need to be such a jerk all the time now that he knows his own worth.
Apart from that. Surprise!Bruce! That was the best :-) I liked the references back to the Avengers movie, seeing the scriptwriters trying to maintain some continuity, or at least remind us that IM3 isn't happening in a vacuum.
I'd managed to avoid all but the very first trailer so had virtually no idea what was going to happen. When Extremis was mentioned towards the start I thought "hello, here we go, iron suit not enough for Tony but he has to take this stuff as well" but it didn't play out anything like the comic storyline which was good!
And then Star Trek. Once again I'd avoided just about all spoilers; I knew BC played a character called John Harrison and that was all. Didn't take too long for the penny to drop, though; when Spock first mentioned the needs of the many outweighing the needs of the few I had an inkling of the direction we were being taken. Nice riff on one of my favourite villains from the original series though.
It's a very full-on movie. I'm still not sure that I buy the Spock/Uhura thingy but that's more because of my attachment to the Spock of TOS than the way the characters are played. Scotty was a lot more believable this time round, although still played for laughs at times which annoyed (again). But wtf was Carol Marcus all about? Seriously, what was her point? Did JJA suddenly realise he only had one female in the whole movie? Because she was extraneous to the plot, and I can't see a valid reason for her being there, other than to re-use a name from TWOK just for the hell of it.
Nice bit of role-reversal towards the end, with Kirk being the one to save the ship ("You'd have done the same." Yes, we know!) And just as well he did; I got more emotional over the near-destruction of the Enterprise than I did over Kirk's death. All in all it was a fun ride, and I'm definitely seeing it again.