Ford,
Watching it now is like knowing how a magician does a particular magic trick. It takes all the 'magic' away.
I saw the BWP when it was in limited release in LA back in the day (1999?). The now wife and I, got tickets via a friend and only learned about the premise from people waiting in line. We had no clue about it being a real film. All we 'knew' at the time was that it was a collection of footage from a bunch of missing college students. So we were primed for the intent of being gullible, and we were.
At that time in film history, nothing like this had been done before. It was truly groundbreaking. Needless to say, people were so scared that they left the theater. In a packed house, I would say about 20-25 freaked out watchers left. Not bored, but freaked. I would equate it to being in a movie theatre circa 'Exorcist' or 'Jaws'. By the time I saw these movies I was older and a little jaded. Thus they were comical.
When released before the truth, the BWP hit its mark in using subliminal scare tactics. Im sorry you got to see the plastic teeth on the movie vampire so to speak. We we scared to death until a few day later when we learned the truth. But a what a fun few days!