AA takes old stuff and reconfigures it into new stuff, like Chantry. They combine wit, meaning, often asymmetrical layouts, good typography, and visual balance to often create really cool posters. Maybe it takes design school to recognize these things, maybe not. They are generally lacking in skulls, flames, stretched and curved computer type, centered layouts, lack of negative space, and naked ladies, which seem to be the hallmark of much poster design.
Some people dig the designy approach, others like the skulls and centering. Its a matter of taste I suppose.