I saw it recently at a preview. I'd forgotten we had a thread and that I'd responded well to the trailer. Good trailer that! Average film though. I don't understand how it's getting such good reviews.
Ok, it's funny and the characters are great. A couple of the set-pieces are fantastic and the premise is strong for a comedy set-up. Dialogue is memorable and the cameo is great fun (possibly cameos, but I never saw the original so wouldn't recognise some).
But the plot is poor. You shouldn't expect much from this kind of film, but what I mean is the insufferable, insulting and thumpingly predictable beats. The story, such as it is, is continually abandoned for cliché after cliché: They bully one another; then the awkward one gets help from the confident one; then the confident one gets embarrassed about being dumb and the awkward nerdy one helps him; then they fall out... yawn, fricking yawn. All this shit is going on while a mildy amusing farce about drug selling in the school is allowed to drift. Even then it's guilty of some awful contrivances to force scenes to fit together.
Honestly, none of this would really matter because it really is funny, but what pisses me off is that my favourite comedy of last year (Horrible Bosses) was funny and stuck to its albeit silly plot. It hung together well. Yet both Hangover II and this reviewed far better.
21 Jump Street is nothing special. It's a good laugh and I recommend it, but lower your expectations and remember the writers think you're a toddler, then you'll have a good time.