We went and saw Pineapple Express last night and I almost pee'd my pants from laughing so much. You fall love the characters almost right away so you're pulling for them from the second they come on screen and if you've ever smoked weed in your life ... you'll totally understand the rambling, cohesive in-cohesive conversations the characters have with each other. Ahh good times. Good times.
I will say that the movie has over the top violence (which I would have preferred to be a little more slap-stick) with a lot of pain and lots of death but you're laughing so much you don't mind how hardcore it is. :)
I also wish they had taken the chance to be a little political. There were plenty of opportunities to throw in a little lefty marijuana politics ... but maybe the kids these days don't care about that stuff anymore ... the best part of the movie for me is watching for all the Freaks and Geeks actors that pop up in the movie. I'm always happy to see them... I miss them.