I read a lot of thumbs down reviews but Mick LaSalle form the SF Chronicle liked it and I often agree with him.
The downers, some from QT fans, said the first part of the movie was boring. Are they right or just one dimensional?
It starts out very diffusely. Pretty much just all the various characters doing their own thing, though Rick and Cliff often touch base due to their friendship. Then things start to slowly come together as the various characters meet and interact towards the final scene at Rick’s.
Part of the movie is following Rick’s precarious arc as an actor. Another is watching Cliff getting by and dealing with all the characters he runs into. A sliver is following Sharon Tate and only because you know who Sharon is and what you expect to happen to her. (Ironically, knowing who Sharon Tate is _before_ you see the movie helps you enjoy it more than if you don’t.) Their threads come together at the end.