I just saw Django - the closest to release day I've seen a move in ever - and I thought it was solid. The most important part, for me, was that it in no way tried to downplay, trivialize, or exploit the horror of slavery for any purpose but to be as gut-wrenchingly awful as it really was. There are sections of the movie that should be hard to watch even for a wizened gorehound like myself, not because the blood is so over-the-top (that part makes the gunfights spectacular and fun) but because we are unmistakeably witnessing an entire system that forces people to become evil, and rewards those who enjoy being evil the most.
Everything else is somewhat incidental - this movie could not have been good if it didn't face the morality of its subject matter head-on, and the fact that it does is probably the most important thing about it. Otherwise, as a movie, I'd say the ending is very predictable - which it's kind of supposed to be, but that doesn't make the last fifth of the film any less plodding. Everything up to that is really great, though. Basically, every part of the movie that has Christoph Waltz in it is fantastically fun, because he's a genius.
Oh wait, spoiler alert.