I watched this documentary today and its good. Its Bob Marley's story told through the eyes of those that knew him well. His wife, his kids & The Wailers especially, have some very interesting things to say about him. It doesn't paint him as an angel or the next guy that was going to change music. It just tells you his story and you make up your mind.
I left the cinema with no doubt he was a legend, and not just some built up musical icon. There is footage of what I think was his only concert at Madison Square Garden. Wow. Good stuff! It runs 145mins and there are moments of the documentary where you will lose focus. However, if you met anyone great and they told you their whole life story, you will lose focus at some point.
If you listen to Bob Marley, you have to watch this. If you're not a fan of his, skip it.