Viewed on DVD...
I don't usually like pot humour. Nothing to do with the drug itself, which I've been around plenty, especially during my school days. (I was the sober wank in the corner.)
It's just that pot humour is so VERY needy. It SO needs to believe in itself, to make so much more of the routine consumption of a mild narcotic that is neither a true stimulant, nor a true hallucinogen, nor a true depressant and that mostly induces people to, say, slowly blather on about the comparative strengths of the various seasonal story arcs of their favourite TV shows.
I liked Pineapple Express in that it more or less owned up to the tedium of pot, of scoring it and dealing with somebody on it. And the movie largely avoided the scenes of hyperbolic highs that plague similar efforts.
Still, the pot humour mostly fell flat. As did a lot of the dialogue, even the ad-libbing.
Seth Rogen is becoming more and more tiresome with each movie, but is still basically a winning presence. (His laugh irritates me no end.)
Without a doubt, the highlight of the film is its physical humour. It goes all the way in its commitment to harsh physical comedy, and towards exploding the conventions of the action film. That's where it sings. It also provides a close-quarters free-for-all that I would personally rank above the Raising Arizona trailer home melee and just below the antics of Clouseau and Kato in The Pink Panther Strikes Again, which is to say, very high indeed.