My knowledge of the original Star Trek is limited, so it was not immediately clear to me that James Tiberius Kirk's past had been dramatically altered. At some point, it hit me that Kirk had a brother that was now non-existent. Vulcan was destroyed. Spock's mother killed. I knew this was not part of Trek's history. My assumption was, given the plot involved time travel, that a reset would take place and the movie would realign with the canon we know. It was not to be the case.
I'm not entirely sure how I feel about the reset, so to speak. It's odd to think forty years of history has just been obliterated. On the other hand, the more I think about it, what I invested so much time in did happen, it just may not happen again. If I recall correctly, it's Uhura who mentions an alternate reality and I suppose that is what we are seeing here. It's not a bad thing or a good thing, but JJ's "What if?" realized with studio backing and put on the big screen.
The characters haven't really been altered. The Spock/Uhura relationship surprised me, though Spock's comment to her about not assigning her to Enterprise because he didn't wish to show favoritism made me suspicious that we were missing something. I'm not entirely sure how I feel about the relationship, but I was immensely relieved we avoided a Kirk/Uhura hook up.
The film was well cast and the next generation of actors ranged from good to excellent in their roles. Chris Pine didn't dominate the screen as one might think considering, in some respects, he is the star of the movie. Mercifully, he doesn't chew scenery as his predecessor had a habit of doing. Zachery Quinto had the toughest role to assume - a largely emotionless character and arguably the fan favorite of the original series. Add to this, he had to act opposite the man who created the role. He's no Leonard Nimoy (who, along with Bruce Greenwood as Captain Pike, added maturity, dignity, and gravitas to the film), but no one is jumping to mind as being better suited for the role. Karl Urban I felt at times tried too hard to imitate DeForest Kelley and thus I was more aware of that then his performance. Anton Yelchin, John Cho, and Zoe Saldana had more leeway in creating their roles since Checkov, Sulu, and Uhura were supporting and less defined character over the course of the TV series and films. (And I loved they were smart and full of initiative rather than mere button pushers.) Simon Pegg as Scotty I felt was the best bit of casting. In a smaller role he was able to quickly establish who the character is and remind us of the Scotty we knew, yet it never felt as if he was trying to copy James Doohan's performance.
As for the rest of the cast of characters, I didn't realize until the credits were rolling that Rachel F***ing Nichols was Uhura's roommate. The lack of acting ability should have been the tipoff. What happened to Winona Ryder's career? I like Eric Bana, but he didn't do anything extraordinary here. And Nero's motivation for destroying Vulcan, Earth, the Federation, and billions of lives seemed rather weak. Spock and the rest of the Vulcans were doing everything they could to try and save Romulus, but the sun went supernova before Spock could get there in time. Jennifer Morrison (Kirk's mother) can really act! She had better material in a few minutes than in the last two seasons on House.
My complaints about the film are relatively mild. Little Jimmy Kirk stealing the car and nearly killing himself was extreme and unnecessary, imho. At times, some of the humor felt forced rather than organic to the story. And, I swear, JJ was trying to pay homage to Rambaldi with the Giant Red Ball of Doom. My mouth fell open when I saw that thing. It looked ridiculous on Alias and looked about the same here.
Finally, I don't care if he just saved Earth and the Federation, no one goes from Starfleet cadet to captain in the spam of a day or two.