There were a few loopholes in the story but that is not the first time in any trek movie or tv show.
The new actors were all right, but there is room for improvement. Their characters were not the same, but they had different life experiences, so it was acceptable.
Still i will miss the mischief in Kirks eyes (very, very much so). (I can't think an actor in his twenties who does have it like Shatner has, well there is Misha Collins but he would have been a little too old for the cadet Kirk part)
My biggest problem was with the Spock/Uhura relationship: it came out from nowhere and did lack of chemistry. Nimoy and Nichols had it, but Quinto and Saldana not so much.