So I watched the What happened, Miss Simone? documentary last night... wasn't that good. If you already know a bit about Nina Simone, you don't really learn anything new, it just felt like a string of concert snippets and interviews, mostly in chronological order (and a lot of them have been on youtube for years). You don't quite get an understanding of her mental disease, how it came about, how it was dealt with, etc.
I think Amy is a much better woven story, attempting to piece together many accounts with a well-structured result.
I find it very difficult though to judge Amy objectively, because I realise that I fill in the gaps in the movie, with all the interviews and concerts I've seen since I became a fan.
It's very hard for me to imagine what it must be like to see Amy if you only knew a few of her hits. From what I've gathered, it really does make you feel like you're seeing a new side of her, not just the caricature. But hard fans like us, we already knew that about her....