How about the cinematography, editing, and style?
I watch a lot of docs, and I found this one to be quite good- much better than I was expecting given the sensational plot summary. I was confused by the ending at first, but then I felt that the PI was being used for a kitschy, tongue-in-cheek ending. The directors weren't expecting you to expect to see anything. I feel the director handled the material fairly, but that's not what this post is about.
The entire time I was watching it I was very impressed with the beautiful shots, the amazing editing and the way it was paced and delivered. I'm surprised there aren't any comments to that effect.
I thought the quick, two second expressions they showed Adam giving in between other interviews, reenactemnts, or after his own dialogue, is a great example of the unique creative devices they used (that also served a purpose). Also, when the voiceover's tone changes to fit a telephone, or someone else speaking- I thought that was creepy in just the right way. I'm just mentioning some small things that stuck with me- but overall a brilliantly shot and edited piece. I never know why some doc receive a lot of attention/awards and others don't, but this was a great doc.