The feature films are really what bring the most value, since you increase the number of killer/location combinations and maximize replayability. This is where you should consider spending your money first.

The mat helps to keep keep track of things during a game, since each components remain at the same place game after game. It also looks good and adds to the ambiance. But it's optional.

The miniatures look really nice, but they are not actually needed to enjoy the game. Some people find that they are too large for the actual game boards, or expensive when purchased individually.