12 Years a Slave

I've been reading and listening to discussion about this film.  Terry Gross interviewed Steve McQueen who explained why he wanted to make the movie:

[My wife] found this book called 12 Years a Slave, and I read this book, and I was totally stunned. It was like a bolt coming out of the sky; at the same time I was pretty upset with myself that I didn't know this book. ... Slowly but surely I realized that most people, in fact all the people I knew did not know this book. I live in Amsterdam where Anne Frank is a national hero. She's not just a national hero, she's a world hero, and for me this book read like Anne Frank's diary but written 97 years before — a firsthand account of slavery. I basically made it my passion to make this book into a film.

Gross interviews the historian David Blight who says,

[I]t's important for Americans to remember this history…because, to be quite blunt about it, most Americans want their history to be essentially progressive and triumphal, they want it to be a pleasing story. And if you go back to this story, it's not always going to please you, but it's a story you have to work through to find your way to something more redemptive.

Leonard Pitts says, “The film is not just brilliant. It’s necessary."

I don’t, for the most part watch violent movies, and from what I hear, this film will be painful to watch. Has anybody seen it?  What did you think?