Well its like comic book movies really. I have never actually read the comics and never got really into the universe these comic book heroes inhabit. Undoubtedly these hollywood tentpole movies are pissing all over canon created in these comic books and somewhere on the interwebs the comic book geeks are no doubt up in arms about god knows what.
Trek fans are no different but what I do know is that if you listen to these hardcore fans your movie is probably gonna suck. 99% of people are not aware that Chekov should be like 10 years old in the reboot, what I do know is that people watching a movie without Chekov will think... 'Where the fuck is Chekov?!' (Oh well, you know, its 2258 and hes...alaaalla...who cares, really?) etc :P