While Tris' struggle to not reveal that she has a multi-faceted personality is the primary dilemma of the story, there's a greater plot at work. Abnegation, the servant class, are also in charge of government, because they actually still take the term "public servant" literally. Erudite, however, think the smart ones ought to be in charge, and are working to smear the Abnegation folks in charge and replace them in the leadership role, which would throw the society out of balance. And with all that going on, they still have time to worry about Divergents, though they don't seem to worry at all about the actual Factionless, who are basically all beggars feeding off scraps. It is the conservative stereotype made real - every homeless person literally is someone who simply didn't want to work...within a Faction.
I've been a fan of Shailene Woodley since The Descendants and (particularly) The Spectacular Now, whose main lead Miles Teller (the future Reed Richards) is here again too. Online fanboys deride her for not being sufficiently hot, but the fact that she looks like a real-life attractive girl makes her more appealing to me than some Barbie-styled model type, and allows the viewer to focus more on her actual performance than sitting there like Beavis going "Boyayoiayoing!" (Teller's character is here to tell her how non-hot she is, which is a funny bit of meta-commentary even if it was unintentional.) She's not the ass-kicker Jennifer Lawrence has been lately, but I suspect that if we get to all three movies it'll be a very different performance by the end, as it is one which grows and changes even in one film. She's the movie's greatest strength, and almost enough to recommend it...but if you're a fan of hers, you know full well she'll be in a lot more movies, and there'll be plenty of chances to watch her in better ones.
So there you have it. Divergent is not the movie for me. But if you find yourself still stuck in an adolescent world of cliques, and think you're the only one who uniquely feels as you do - well, this may be empowering. Though not as much as the eventual truth that none of that stuff really matters for long.