I saw this movie the other day and I thought it was great. It was quite possibly the funniest movie I've seen so far this year, and definitely ranks high on Seth Rogan's list of comedies.
I had two friends who hated it, though. One of them hates Jonah Hill, so he immediately proclaimed his hatred for this movie for no other reason other than the fact that this actor was in it. The other friend thought it was predictable and boring, but he loves the Resident Evil movies and he thought Hansel and Gretel was one of the greatest movies of the year. Take those opinions as you will.
Personally, I couldn't stop laughing. Yes, some of the jokes are juvenile, but if you're going to see this and expecting high art, you need to get your head checked.