I personally think that the whole idea that the new Trek film happens in a sort of "parallel dimension", and that the original Trek timeline still exists (within the fictional universe) to be more an attempt to appease Trek fans angered by the loss of the original chronology, and doesn't make sense when you look at the actual plot. Were the writer's talking about that parallel universe idea before the film was produced, or did it only come out after reactions from fans?
When I saw the film originally, I took the mention of an "alternate timeline" to mean that the past has been altered by Nero, but that this was still the same universe the other series happened in. But now, that future had been potentially erased by Nero's interference. Indeed, Spock says, "Whatever our destiny's might have been, that has been changed."
What is so shocking about the destruction of Vulcan and the death of Spock's mother is that Nero has travelled back in time and destroyed the things that Spock held most dear, and forced Spock to sit back and watch. He also robbed Kirk of the chance of ever knowing his father... both of our principal characters suffer a great loss that affects their lives. Yet, if this is all just a parallel universe of some sort, then Nero's actions as the antagonist are not as emotionally powerful, as Nimoy's Spock would be aware that Vulcan was still well in the "universe" he comes from - there is less of an emotional stake for the audience, in my opinion.
So, if this is indeed the past of the same universe, why didn't elder Spock's memories change when Nero changed the past - why does he still seem to remember events of a timeline that no longer exists? The same question could be asked of why, when Marty McFly travels back to the revised 1985 in the end of Back to the Future, he still remembers how his parents were in the original timeline, when he changed the past back in 1955. Some might argue that this is because he is in an alternate universe that split off from the original one, but I prefer to think of Spock and McFly having their memories as just one of the necessities of a time travel story, for the plot.
i understand how fans of the TOS films, TNG, DS9, and Voy feel about a time travel story altering the Trek they love, but from a storytelling sense, I think the intention was that Nero had made major changes in the lives of young Kirk and Spock, yet despite a shattered timeline, destiny somehow found a way to bring the crew of the Enteprise together, against all odds.
How do others feel?
(...PS, people will argue - if this is the past of the regular universe, why doesn't Spock just go back in time and fix it, like Picard did in First Contact? My feelings are that the space-time continuum has been fundamentally altered in some way, by all the time travelling since the temporal cold war, that time travel is no longer possible ... there is no reset button anymore...)
When I saw the film originally, I took the mention of an "alternate timeline" to mean that the past has been altered by Nero, but that this was still the same universe the other series happened in. But now, that future had been potentially erased by Nero's interference. Indeed, Spock says, "Whatever our destiny's might have been, that has been changed."
What is so shocking about the destruction of Vulcan and the death of Spock's mother is that Nero has travelled back in time and destroyed the things that Spock held most dear, and forced Spock to sit back and watch. He also robbed Kirk of the chance of ever knowing his father... both of our principal characters suffer a great loss that affects their lives. Yet, if this is all just a parallel universe of some sort, then Nero's actions as the antagonist are not as emotionally powerful, as Nimoy's Spock would be aware that Vulcan was still well in the "universe" he comes from - there is less of an emotional stake for the audience, in my opinion.
So, if this is indeed the past of the same universe, why didn't elder Spock's memories change when Nero changed the past - why does he still seem to remember events of a timeline that no longer exists? The same question could be asked of why, when Marty McFly travels back to the revised 1985 in the end of Back to the Future, he still remembers how his parents were in the original timeline, when he changed the past back in 1955. Some might argue that this is because he is in an alternate universe that split off from the original one, but I prefer to think of Spock and McFly having their memories as just one of the necessities of a time travel story, for the plot.
i understand how fans of the TOS films, TNG, DS9, and Voy feel about a time travel story altering the Trek they love, but from a storytelling sense, I think the intention was that Nero had made major changes in the lives of young Kirk and Spock, yet despite a shattered timeline, destiny somehow found a way to bring the crew of the Enteprise together, against all odds.
How do others feel?
(...PS, people will argue - if this is the past of the regular universe, why doesn't Spock just go back in time and fix it, like Picard did in First Contact? My feelings are that the space-time continuum has been fundamentally altered in some way, by all the time travelling since the temporal cold war, that time travel is no longer possible ... there is no reset button anymore...)
I have more of a life than that.
I hear you...canon is for organizing things, not for carving rules in stone. Everytime someone says "that violates canon" or worse yet shouts "TEH CANNON!" I die a little bit inside. I mean, it would be one thing if Captain Picard was suddenly a mermaid wearing a tutu driving a Volkswagen...but Captain Kirk's eye color matters not in the grand scheme of things. 
