It's not good.
It's also not AS bad as you've heard.
But yeah, it's very very not good.
If it makes money, Shayamalan might be "back" jus because he'll have "proven" he can handle an FX-driven feature. If not... yikes.
"Intermission" has more elaboration about Twilight and such: http://www.escapistmagazine.com/articles/view/columns/moviebob/7779-The-Problem-With-Twilight