Very disappointed. Pike, Spock and Chekov were pretty good, McCoy was OK, but the story was too simple and I didn't like Kirk's insubordination (they have a ready room so that there aren't debates on the bridge). Disappointed in Ryder's cameo and Nimoy was hit-and-miss; he should have obviously recognized that Kirk was probably too young to be good friends with him. Nero's ship was cool but his motivation was weak given that his world could have been destroyed without Spock accidentally contributing. What was he doing for 25 years? I would have preferred that the Federation actually did become somewhat corrupt and reprehensible, and perhaps that he had regular time travel ability (the ENT forum suggestion that he was Future Guy).
I also wonder if this film wiped out the other timeline; both the alternate-universes and the single-changed-universe theories are possible. I certainly would have preferred it to have been an ordinary prequel in the existing timeline, just having the Enterprise be an established ship rather than on its maiden voyage.