I wasn't a big fan of THREE BILLBOARDS either. I was looking forward to it because from the trailers it looked pretty funny. Same as you, I was caught off guard with the change in tone as the film progressed. I thought Frances McDormand was good and deserving of her Oscar. I like Sam Rockwell too but wasn't as convinced with his Oscar win. I believe the movie is more hype than anything. Not a bad movie in my opinion, but not as great as what some of the critics have given it.