Well, just got back from seeing it. I enjoyed it a lot, though I'll really need a second viewing to let everything sink in, but I'll give my first impressions. Beware of spoilers because I freaking hate micro-sizing text(we need spoiler tags like every other forum on the internet).
Things I didn't like: We'll start with these first since there are few. First off...poor Scotty getting thrown off his ship for having a conscience. It really pained me because Scotty's always been my favorite. Secondly, the poor ol' Enterprise just takes a f***ing pounding without really dishing it out. I really, really, REALLY hope that in #3 they'll give the Enterprise some badass moments of kicking ass and taking names. Thirdly...I really am not sure how I feel about the Enterprise's new impulse deck. I think it takes up far too much room, although the inconsistencies with the Enterprise's size also seemed a bit more magnified with the torpedo bit. Finally...Pike.

Things that were meh: John Harrison = Khan. Okay. Couldn't have at least had a throwaway line about how he underwent cosmetic surgery? Also, the explanation of Khan's blood could've been expanded on slightly. Also, Scotty didn't have nearly enough glasses of scotch there.

And finally, the reactor scene. Could've been changed up a LITTLE more so it didn't feel quite so ripped off.
Things that were awesome: I'll start off with this one. Pike's death. I hated it and liked it at the same time. I hated it because I hate that he died. I liked it because it was something that Kirk needed. He needed the hero's journey and part of that is the death of the mentor. Kirk's reactions were a bit quick, but I can easily imagine him sizing up the situation and becoming that hardened and determined, and I really felt like this was like him losing his father again. The new warp effect is AMAZING. The Enterprise needed a trail and it got a neat one. Also, while I would've probably preferred the warp core from the game, the one in Into Darkness was pretty damn neat and actually looked like a reactor rather than a glowing tube. I also loved the ships in Marcus's office(XCV Enterprise, Phoenix, NX Prototype, NX-01 Enterprise, Kelvin, and Vengeance), really made it feel more Trek. I liked the subtle references, such as Sulu taking temporary command of the Enterprise and enjoying it and McCoy performing surgery on a torpedo. I loved the interaction between Kirk, Spock, and McCoy before Kirk makes up his mind to open up one of the torpedoes. I really liked how tastefully edited Marcus's death scene was. What we don't see, we can imagine even more gruesomely than the movie's rating would've allowed. The Klingons were awesome and, if I'm right, that was authentic Klingon language used too. Kirk finally got to kick ass instead of just getting it handed to him, and Spock finally got a hard, physical fight scene. "One day I've been off this ship, one bloody day!" Cat women. The entire thing at Nibiru. Dr. Carol Marcus was fantastic and I hope she'll remain a member of the crew. I really liked that they didn't KILL Khan. Always think killing off your villain is shooting yourself in the foot. Old Spock!

And finally, the 5 year mission begins as it should: "Space, the final frontier. These are the voyages of the starship Enterprise. Its five year mission: to explore strange, new worlds; to seek out new life and new civilizations; to boldly go where no one has gone before." I was grinning like an idiot at that part.
There's probably more that I'm missing but it can wait until I see it again.

EDIT: Also forgot. PRINCESS BRIDE REFERENCE! Kirk was only "Mostly dead".