I had a blast, my fiance hated it.
I guess it depends a lot on expectations going in - I had none, my fiance thought it was going to be a creepy scary film so she was disapointed and found it stupid. Though I also think my wee crush on Kristen Connolly throughout the movie might have made her bias on disliking it.
I think someone else mentioned it that the movie is really a 'Monster Movie', I'd have to agree - it really reminded me of a more adult/gory spin on The Monster Squad from way back in 1987 in the way it was self-aware, more about comedy and having fun with lots of monsters.
That said, I don't think it was a big revolution in horror or anything, and it's not quite as clever as it thinks it is / wants to be - of course that might be me digging too much, I always find that self-awareness is great and poking fun at the tropes is good fun, but when a movie (or even a game, take Bioshock for example) takes that approach, it inevitably falls victim of some kind of double standard to an extent, as to mock the tropes, it has to repeat them to a degree. I'd say that the original Scream to my mind was much cleverer and more successful in the 'meta' approach.
To my mind it's just a great fun monster movie.