Give it to a teenager/adult who likes RPG's, but not to children.
...Eh. Pretty dead-on, but calling it "teen angst" implies that the main concern is something trivial, which is simply not the case. You'd be pretty shocked/sad too if you were locked inside the Yamanote Circle by the government, demons were attacking you, and you could see that nobody trapped with you has long to live.
Devil Survivor does contain information on landmarks within the Yamanote Circle, but keep in mind that the story doesn't focus as much on the setting as much as, say, The World Ends With You.
Moving right along, it's shockingly easy for an Atlus game, (which is to say that the difficulty is about average) so younger players can grasp it pretty readily. For a game where you tame demons, it actually isn't so scary, since many of the more creepy-looking demons have hilarious messages. (For example, Kikimoras are the spirits of unbaptized children/aborted fetuses, and they look a tad freaky in-game, but their messages in the Devil Auction are mostly about their love of Dia, which is a healing spell.)
There are some good role models in the game, but keep in mind that this is a Megaten game, so there will be no shortage of moral ambiguity.
All in all, I wouldn't recommend this to anyone under 13. The setting is somewhat grim and the monsters can get both cute and disturbing, so it's not a great idea to give this to a kid.