Is it very, very, very violent? Yes, but it's depicting a violent world full of cruelty. It needs to be violent.
Does the word "nigger" get thrown around a lot - yes, it does, but only in situations where it would be used and any other word would have come off as awkward and/or wrong.
What makes the film work is the development of Django as a character. He slowly builds up strength and knowledge and rage until it explodes in the only way it can in a Spaghetti Western.
Christopher Waltz is also brilliant as the only non-American character in the film (other than a Tarantino bit role) who sees the horrors of American slavery through the eyes of someone who can't culturally understand it at all.
DiCaprio finally proves he can actually act and does a delicious turn as a bad guy.
What may not be clear to people who have not seen the film is that not only is it moving and touching, it is also hilariously funny. This is why the violence doesn't burn too badly - it's hard to be too horrified after belly laughs.
The cinematography is excellent - this is a film to see in a theater and not at home. Quite frankly, it's beautiful.
Is it a film that will leave you uncomfortable at times? Sure it is - but that's what a film about slavery should do.
Is it racist? Not in any way, shape or form.
It's simply brilliant and one of the best pieces of American cinema I've seen in years.