It was high time Tarantino made a western seeing his love for the genre that you can see in his other films. However, I feel this isn't really a western. No, this movie is actually closer to a myth. Set in the American West. Now before you murder me for my nonsense, let me explain.
The Western's archetype is a lone hero coming to a place he doesn't belong. Because he's badass, he brings back order in a messed up place then vanishes back into the wild where he belongs. The iconic ending of The Searchers is probably the best example of this. There's actually little character evolution in a western although the character will face setbacks.
But in Django Unchained, we have a true initiation story. Our hero starts low, encounters a mentor who imparts his knowledge to his talented student before they go together to face a great evil. The mentor is not enough and fails but his pupil is now armed to defeat the evil on his own. Django's character is closer to every padawan in Star Wars (ObiWan episode 1 ; Anakin against Doku ; Luke episode 4/5/6) than any true Western hero, he replicates the tale of Siegfried and Brunhild.
The film isn't perfect though. As always, I think Quentin Tarantino is too heavy handed in the big fights. I heard in an interview that he does so because it's supposed to make us laugh rather than be realistic. But it doesn't always work.
It makes me laugh when Django unexpectedly blows up Tarantino's character because he's holding dynamite, or when we have to "Tell Miss Laura goodbye". However I think five bullet wounds painting the entire hallway red with geysers of blood is not specially fun, just ridiculous. Sometimes this kind of ultra-violence is to take the audience out of the scene to remind them 'don't worry, none of this is real' but here it's unnecessary. We have already seen much worse earlier in the movie.
Quick note on blowing up the whole plantation of Candieland with 2 bags of dynamite whereas 1 bag exploding made only a very small hole : As I said, Django Unchained is more a mythological story, ending it with a blast is part of the myth.