I saw this last week and thought I'd better review it, especially as I started the thread so long ago! Chris Pine manages to make the role of Kirk his own, yet still allows flashes of the Kirk-like humour and irreverence. The scenes in the training simulation are particularly humourous and made me laugh out loud. :D
Zachary Quinto's performance as Spock is equally well-interpreted - perhaps more so than Pine's. The elaboration of Spock's formative years is welcome, however, there's a non-too-subtle attempt to draw similarities between Kirk and Spock's respective 'rebel' tendencies (read: they were destined to be friends). That said, Quinto's struggle with his own humanity works well amongst his intolerant Vulcan counterparts.
Unfortunately, beyond that, the screenplay takes a slightly "kids in space" feel, reminiscent of some horrible mutation between Space Camp and Starship Troopers. It sorta works on it's own merits, but it cannot carry the mantle of Star Trek - there's just too much tradition and... dare I say it.... 'values' that have been pushed aside to make it acceptable to a wider audience.
I think that disregard is almost inevitable given the use of the whole 'parallel universe/alternate timeline' premise. It's a somewhat weak way of freeing the director from canon without going for a full reset. The wholesale destruction of the Vulcan homeland seemed extreme (especially how that will almost certainly imbalance any future sequels), as was the death of Spock's mother, Amanda Grayson. 'Old' Spock being stranded in this alternate timeline also feels disappointing.
I dunno. I enjoyed it as an action film, but it's very much a different beast from the Star Trek franchise.