This really is essential and must-see if you have any interest in the popular music that was created in the mid-60's - mid-70's in Southern California, specifically, the artists who lived in the Laurel Canyon area. I'm not an expert in this, but I am pretty knowledgeable about it, so it's always a treat when I learn about things for the first time that I didn't already know. A mild criticism of this movie was that it spent precious time on Little Feat, which was noted in the documentary itself that they were not a very popular or well-known group. The movie also reminded me of how great Linda Ronstadt was before she made the puzzling decision to start singing songs from the Big Band Era.
If you like this movie, I would also recommend 2008's, "The Wrecking Crew" about the unknown session musicians of that era who were responsible for helping to make many of the classic songs that came out of that time.
Finally, please note that this great documentary should not be confused with "Echo in the Canyon," Jakob Dylan's self-indulgent documentary that ostensibly was also about the Laurel Canyon era, but instead was mostly just him and his buddies doing covers of classic songs made famous by the original artists.