I suspect Black Snake Moan will take a while to be appreciated for what it is. In fact, it may never be.
Everyone, including the advertising materials, describe it as the story of a religious man who chains the town slut to his radiator to cure her of her fallen ways. This is the most salacious story element, so I see how it happens, but ultimately that's something like saying "Macbeth" is the story of a man who hires assassins to kill his comrade. It's not inaccurate, but it misses so much.
Roger Ebert's review compares it to Road House, for their similarly off-the-wall unclassifiable quality. Apparently, on Ebert and Roeper, guest critic Kevin Smith compared it to the writing's of William Faulkner (some of the aftermath of that here).
I'm inclined to agree with both of these comparisons in their way.
This is a trashy movie, but it's like it's out of the time when many trashy moviemakers were struggling to make something good, too. Obviously there were many failures in this, including many, many examples where they failed to achieve either goal.
Black Snake Moan will likely fail people who aren't able to take substance with their trash. It does get slow and thoughtful. And realism being the most expected and overrated dramatic crutch of the modern age, many people will criticize (and have criticized) it for its lack of naturalism in tone and acting.
They are and will be missing the point entirely.
This is a fearless movie.
It's unafraid of being dismissed as trash. It's unafraid of being laughed at. It's unafraid of challenging or confusing.
The performances are likewise fearless. Samuel L. Jackson and Christina Ricci were clearly unafraid of going completely into his character and taking that to wherever it takes them. Justin Timberlake was unafraid to be completely ineffectual and pathetic.
I'm not prepared to call it a great movie, but it is a movie that does the things that great movies do. It attempts to entertain, challenge and shine a light on its subject without clear judgment and allow us to consider and add meaning to the events we've seen for ourselves.
Just to clear up a factual concern, Rob Nelson's review refers to "a talking blues sermon about the hellfire horrors of abortion." I cannot make clear enough how inaccurate this is. This song is not anti-abortion, or political or religious on any level, it's an emotional expression of his feelings regarding his wife having an abortion without telling him. It's actually quite a beautiful scene.