This is how I felt when I saw Ocean's Twelve in theaters. Ocean's Eleven was a joy to watch...but its sequel was clearly about the creators having a lark without bothering to make it entertaining for the audience. There are certain scenes where you can see the writers laughing their butts off without considering that it isn't funny at all for the rest of us. It's like that kid that starts laughing at his own joke before he can finish it, making an uncomfortable experience for the rest of us watching him try to compose himself.
Cabin in the Woods is not that. Admittedly, director/writer Drew Goddard (Cloverfield) and writer Joss Whedon (Firefly, Buffy, Avengers) are having the lark of larks while presenting this horror movie, but it's also a love letter to us horror movie junkies. They clearly know the landscape of horror movies and they navigate it easily as they deconstruct it. Similar to how Scream disassembled the thriller/slasher flick even as they lived it, Cabin does that for the horror genre.
It's not a work of art. But bottom line, it's fun. It's filled with so many winks and nudges that if Cabin were a person, it would look like it was having an epileptic seizure. I'm still not certain as to whether some of the plot-lines are over-the-top ridiculous or over-the-top hilarious.
However, I think it's a must for any of us that grew up in the slasher/old horror movie monster era. It's a movie that encourages multiple viewings...and the less that is revealed about the plot, the better. In fact, don't even watch the trailer. Just go see it. It's a mixture of laughs and some old horror movie tropes that are dissected. Some of it doesn't make sense, but who watches a scary movie for logic?