Great movie, just saw it. I also enjoyed the whole time-travel/alternate universe thing. It'll mean they can play around with and re-explore that classic Star-trek era without having to worry about continuity so much. And Winona was in it! What a milf!
My main gripe is the incredible trivialization of black-holes. Those things were lame. I was more outraged by their disrespect for black-hole lore than their fundamental alteration of the Star-Trek universe. Ever since worm-holes came into sci-fi vogue people are just getting a little too cute with the whole concept. Soon they'll be using singularities instead of bin-liners. Or "Hi, come in, come in! Sorry the place is a mess - we had a little party last night and I haven't gotten around to cleaning it up yet. You want a coffee? Oh, watch your step there, Kevin dropped a singularity. Just step over the event horizon, I'll get it later. Cream and sugar?"
Oh, and Eric Bana was definitely too inherently likeable to be a convincing/scary villain, but he is Australian after all.
I liked it a lot, although I was never a fan of 'first generation' star trek, and haven't seen the other movies.
The one thing that bugged me was that the whole red matter thing seemed very implausible - however in that way it's true to the series, lol. So overall, very entertaining and I anticipate the next one.