Hello everyone, I just joined the forum. I am a long time Trek fan, and joined in order to share in everyones anticipation for the new film!
I just wanted to contribute ...
The way I see it (spoiler alert?):
The very premise of the movie (Spock traveling back in time in order to thwart the Romulans' nefarious plans) gives a nod to the "canon" ... and hence should be accepted in the same way that the Mirror universe is. Obviously, Spock traveling back in time from the canonical, post-Nemesis universe is fine (time travel has always been a staple of Star Trek) ... so it seems as though Abrams has anticipated / prepared for this exact debate. Perhaps the movie works perfectly with the established canon, simply because it takes place in tandem with the post-Nemesis world ... thus, the differences in the alternate timeline take place alongside the original timeline, while interacting inextricably with it. Hal, it seems as though you (trying to preserve the canonical timeline) and Spock are on the same side ... both are trying to keep Nero from screwing things up beyond recognition :-)
Also, the "canon" did not exist before TOS ... it came about organically, as new ideas were added, in the same way that I hope this movie will add to an already wonderful sci-fi universe.
Frankly, I see no reason why Star Trek XI would clash with the canon ... we are all sci-fi nerds on this forum: as soon as you introduce time travel to a story, you are going have a very complicated mythology. Infinite Diversity in Infinite Combinations, anyone? :-D