To call it [the "secret"] an anticlimax would be an insult not only to climaxes but to prefixes. It's a crummy secret, about one step up the ladder of narrative originality from It Was All a Dream. It's so witless, in fact, that when we do discover the secret, we want to rewind the film so we don't know the secret anymore.
And then keep on rewinding, and rewinding, until we're back at the beginning, and can get up from our seats and walk backward out of the theater and go down the up escalator and watch the money spring from the cash register into our pockets.
I've read some spoiler stuff about this movie, so I already know what the "big twists" are, and I have to admit, they sound really lame. I think that M. Night Shyamalan really needs to try something new. Yeah, I found Signs really effective when I first saw it, but the thing just doesn't stand up to any kind of scrutiny at all.