He was the greatest F1 driver of all time. This is fact (and the theme of the film).
They did an amazing job given what seems to be a limited budget. It also must have been difficult to find an abundance of footage. The interviews with the man himself were awesome.
The movie did a good job of telling the story of how he came to race and I found the explanation of what happened in 1950 and 1953 most interesting.
A little dry and lacking emotion, the movie isn’t great. Still good though, and recommended. In a nutshell, interesting.