I actually saw Django Unchained back when it first came out, but didn't have the time to write anything major about it. But as I won't be done with Hungry Ghost until next week, I decided that it's better late than never.
This is a Quentin Tarantino film, so before even seeing a single frame you have some idea what to expect: subtle self-awareness, top-notch acting and writing, and brief scenes of brutal violence punctuating a surprisingly deep story. In fact, I think this is not only Tarantino's deepest film, but his riskiest. He's very knowingly and deliberately put himself in the awkward situation of being a white guy writing about racism.
He pulls it off. I would expect no less from Tarantino, but a big reason why he pulls it off is Christoph Waltz. Waltz won an Oscar for his performance, and deserved it, because his character King Schultz is the single most important person in the film. Consider him to be the perspective character for the white audience member, a stranger wandering the land of slaves and plantation owners. Schultz is an outsider by means of being a German immigrant, whereas the audience is separated from the setting by time, but the principle is the same. We know enough to properly identify the heroes and villains, but take for granted what makes them so. Schultz's character arc throughout the movie is his coming to realize just how awful things are. He begins the film regarding slavery as a bad thing, but his distaste is academic and detached, and he's not above playing the system against itself. But as his journey with Django takes him deeper and deeper into the belly of the beast, the true inhumanity of the institution slowly unfolds before him.
The plan to rescue Hilda is perfectly sound, but the genius of it is also its great failing: it's legal. This means that Schultz and Django can pull it off while still remaining respected members of society, but it also means that they have to acknowledge the rightness of the society, or at least pretend to. Schultz is fine with this at first, but becomes increasingly uncomfortable with the prospect of turning a blind eye to the brutality around him. Finally, he's offered the chance to walk away with everything he came for, exactly the victory he planned, in exchange for just one thing: he has to acknowledge that Candie is a honest man, and that the society that he lives in just. And Schultz can't do it. He scuttles his own plan at the very moment of success because, as he tells Django, "I just couldn't help myself." He couldn't go on paying lip service to a society so fundamentally corrupt.
If Schultz is the most important character in the film, the second most important is probably Stephen, Candie's loyal slave. Stephen's first scene is one of the best constructed scenes in the film, because it tells us in a few minutes 90% of what we need to know about the character. We see him sitting at a writing desk, writing out a check to which he affixes Candie's signature with a stamp. Then, through the window, he sees Candie's carriage approaching, and so he goes out to the front porch where he plays court jester, lobbing insults and repartee at Candie's entourage and even Candie himself for the amusement of all. Later scenes establish him as the power behind the throne, smart where Candie is merely educated and subtle where he is brutish.
So, to break down the conflict: we have a black hero and his white mentor/sidekick on one side, and a white villain and his black servant/vizier on the other. What you'd expect from this setup - the traditional/cliche resolution - is that Candie kills Schultz, then Django kills Stephen and Candie, probably in that order. Or, alternatively, Candie kills Schultz, Stephen backstabs Candie in some fashion before dying, possibly redemptively, and then Django kills Candie. But neither is what happens. Instead, Schultz kills Candie - sacrificing his own life in the process - after which Stephen takes over the plantation in all but name and becomes the villain that Django must defeat in the denouement. And the movie is much, much better for it.
Django Unchained is a movie about racism, but it's also a movie about the rejection of racism. It's about the evil that white men do/did, and how that evil is destroyed. Had Django killed Candie, the film's message would be simplistic and wrong: a white villain as the source or avatar of evil, and a black hero restores justice by killing him. Black = good, white = evil. Simple, and completely off base. This happy ending would have been achieved through the demonization of whites, which is merely racism in a different form. Django becomes the man who hunted monsters and became one himself. Instead, Candie's death - and the symbolic rejection of what he stands for - must be at the hands of a white man. In doing so, and accepting his own death as penance for standing by and doing nothing for so long, Schultz earns redemption for his race.
Portraying Stephen, a slave, as a villain on par with Candie is perhaps Tarantino's most controversial choice as screenwriter and director. One could even, if so inclined, see it as of blaming the victim. But the story is more complex than that. As Django was once a slave, Stephen is a slave as well. But while Django has only ever been seen fighting against the system, Stephen has embraced it, sacrificing his dignity in exchange for power. In many ways he's a shadow figure to both Django and Schultz; Django in that a slave's life has affected them both deeply, Schultz in that they both game the system for their own purposes. Stephen would have learned firsthand the cruelties of the society in which he lives - he mentions having seen slaves castrated before - and he went along with it because the society empowered him personally. In Stephen we see most clearly that it is not a person's skin that makes him righteous or corrupt. The society is the source of corruption, and whether individuals are good or evil depends on whether they allow it to corrupt them, or defy it to follow their own conscience and sense of justice.
Django Unchained was nominated for a Best Picture Oscar last year, but ultimately lost to Argo. I never saw Argo, so I'm in no position to say whether or not it's a better film, but Django is certainly a film that deserves respect. It is, as the Library of Congress likes to say, "culturally significant," and one of the deepest and most thoughtful meditations on racism in recent years.