I found this to be an excellent movie despite (or partly because of) major variance from the historic events it is based on.
Up until watching this movie, I had just seen four Tarantino films, so I guess I am not on his bandwagon. But I really enjoyed two of them (Jackie Brown and Pulp Fiction). I can now say I liked Once Upon a Time in Hollywood just as much as I did those two movies.
The dialogue is sharp and the main characters are sympathetic enough so I cared what happened to them. The film is loosely based on actual events, with fictional characters thrown in and at least one major plot change that I won't give away. I think some of the most negative feedback I have seen about this film were from purists who didn't like the major change in the story. But I appreciated the change. If I want total accuracy, I would watch a documentary, but I want to be entertained, not depressed, and I was.
And I plan to watch it again, not just for the sake of the story, but because maybe the second time through I will catch more of the movie references that are supposed to inhabit Tarantino's films.