I can see it like that. I figured it'd just be funny for about a half-hour, then lose its touch. I'm a movie cynic, I mean, I won't even go see Tropic Thunder for the same reason.
Put it this way. I wasn't even high and I was laughing the entire movie. There were several times where the entire theatre cracked up with a big laugh or a huge 'ewwww'. Go see it, it is well worth the 7.50. Well, in my case 15.00 because of a girl.