I disagree with you, Legomancer (but I’ll skip the wrath),
First of all I frequently read two opposing reviews of a movie. Second, trailers today are notorious for making you believe a movie is about one thing then you find it’s about something else.
[pet peeve] Why not make the trailer like the movie or make the movie you are going to advertise?![/end peeve]
To the OP, if a movie is BAD or misrepresented (by the first half) I ask for my money back. And despite what ArchiveGuy says, managers are always friendly and (apparently) happy to refund my money.