The documentary was ok in my opinion. It's biased, but a lot of things like that on Netflix are. To me it highlighted just how crazy people are about college football. We had elaborate sign-stealing schemes and then elaborate "investigative" message board journalism to show everyone what had happened. All of this was done by people with a little too much time on their hands.
I believe everyone on the Michigan football staff knew what was going on. I also believe it was happening in varying degrees in a vast majority of places. In my opinion, the biggest benefit of this situation is it fast tracked direct communication with players on the field like the NFL. As big as college football has gotten with the money flowing around the sport, this was necessary.