It's very rare that DiCaprio is put in a position to be the flashier scene-stealing character, he's usually the straight man that binds everything together (the Nick Carraway role). It will be interesting to see if he can pull it off. I'd have gone for someone like Bale, Pitt or Depp, with Joseph Gordon Levitt as Nick.
And I've just finished watching the first season of Homeland. It's amazing, probably one of the best TV seasons in recent years. I'd recommend it to anyone with an interest in spy/political thrillers.