While I respect classic comedies for what they accomplished in their time, they rarely come off as funny to me, at most being amusing. "Some Like it Hot" is a perfect example- that film, often called the best comedy of all time, certainly amused me, but not once did it make me laugh.
This movie, however, completely flips that on its head with its constant, witty quips and speedy back-and-forth dialogue. It almost never drags, the constant action of the story matching the machine-gun pace of the dialogue. I cannot praise it enough. Hats off to all involved, it just gripped me all the way through.