I've seen three Shamalang movies so far:
The Sixth Sense - I won't say I figured out what the twist was, simply because until the big reveal I didn't realise that it was supposed to be a twist. It starts off with Bruce Willis getting shot in the chest, and then after that, no-one whose alive ever notices that he's there, except for a kid who talks to dead people. I just kind of assumed it was meant to be obvious that he was a ghost from the start. It's like if The Terminator ended with the breathless reveal that Arnie is actually a robot! It turns out that this is a pretty boring movie, if there's no twist in it.
Unbreakable - I have to say, I loved this one. I've always been a sucker for a good superhero movie, and this is a good one. I'm not a huge fan of the Mr Glass twist, but it didn't spoil anything for me.
Signs - The biggest cinematic turd anyone ever shat out onto the silver screen. What Chodon said about the aliens. Plus, nothing the humans did made sense, either.
After that, I've never heard anything about any of his later movies that makes me want to spend the time and money to see them. And I doubt I'm going to bother seeing The Happening.