As for the characters behaving "out of character," I think we're forgetting that these people are younger than we ever saw them in the show. When we first met Kirk, he was already in command of the Enterprise. Here, we're meeting him as a teenager. We're also meeting him in an alternate timeline, a timeline where he didn't have his father around to influence his development. OF COURSE he's going to act like a different person.
I would also argue that Star Trek has never been about "exploring new worlds." It's about using the sci-fi setting to explore the human condition, and I think ST09 did a great job of that! We got to explore Kirk's development from a drunken farmboy to a cadet at the Academy to someone who was put in a very difficult situation and had to take command of a starship. We got to explore it through Spock, from his relationship to his father, to the death of his mother and the destruction of his world. Spock and Sarek, in the prime universe, had a very uneasy relationship. I very much hope that, in this new timeline, we get to explore their relationship from a different angle, now that Amanda is gone.
Yes, there was a lot of silly action, and Nero's motivations may not have made perfect sense, but to say that the movie lacked the spirit of Star Trek is, quite frankly, wrong.