Being a huge John Lennon fan, I find all of the documentaries to be wonderful. They are all very moving, and when you hit the end of the films, you feel very moved.
LENNONYC is a documentary that focuses on the New York years of John Lennon. Obviously that's where the film starts. I felt that the explanation of his time in NYC was really good and the photos and old videos really add to this picture. The music that is incorporated throughout is wonderful because it's all of John Lennon. Some audio was taken from "never-before-heard" tracks.
Overall I feel that this is one documentary worth watching. I don't feel that it was the greatest, as it does get a little repetitive at times. If you're looking for the life of John Lennon, Imagine is the documentary for you. Nevertheless, this does not disappoint.