Secondly, I keep reading a Dave Grohl quote that this is "his most important work" - a sentiment that I scoffed at initially. I mean, isn't Nirvana his most important work? But then I realized that the back portion of the movie is dedicated to showing the joy of playing music together or, if you wanna take it further, of creating anything together with other people. If Grohl can inspire people to do that; it may very well be his important work.
Objectively, it's an enjoyable film. I suggest you watch it.