I just watched this yesterday! I enjoyed it, but I have very mixed opinions on it. The direction and characters were overall great, as they should be with Tarantino. I was pretty enthralled with most of the time watching the movie. It's well shot, and DiCaprio/Pitt are great.
The theme and the Sharon Tate stuff was weird, though. As an alt-history exercise I loved Inglorious and Django. Those felt like they were for large groups of people and fantasies based on events that a lot of people obviously remember and can empathize with. They also don't really rely on outside knowledge to work. You see how the slave owners fucking suck and you see how the nazis suck within their respective movies. With this movie the Sharon Tate murder, while tragic, is just so specific of an event to base an alt-history fantasy on that it's not terribly enticing.
Within this movie Tate is an non-character. Her scenes were charming I suppose, but I feel nothing about her. The Mason group is kinda creepy when Pitt's character goes there, but that's about it. You don't learn enough within the movie. So as you approach the ending I think the only thing really giving tension is knowledge that Tate gets murdered. Then you have the swerve and she doesn't here. They kill the hippies, the end. If you know nothing about Tate then this is just a strange fucking ending. And if you know the ending of the movie then it also doesn't work. One of the few times I think a spoiler could actually ruin the movie in a big way.
Some people talk about it giving Tate the life she deserved or something, but you get none of that in the movie. It's about two other random dudes, not her at all.