Loved the first hour or so (spoilers)
The first half of the movie is just a really good drama with excellent dialogue and performances. I knew there was some kind of twist coming so that was too bad, as it made it impossible to just completely sink into the drama as it seemed to be unfolding. (OTOH I'm not sure if I would have watched it at all if I were not curious about the twist.)
Then we have the big reveal that what we're watching is a movie being filmed. Or is it a reveal? The movie they are making is actually not the same as what we saw in the first half. I think maybe that might have been a better way to go but I can see it both ways. I did miss the characters we saw in the first half of the movie, but things were getting fairly interesting in a different way in the meta-filmmaking story (one of my favorite genres)...until it kind of petered out in the late stages.