A great article with more details about the additional security that Blu-ray employs over AACS. To clear things up, HD-DVD only uses AACS for content protection (AACS is just encryption). Blu-ray takes it to a whole new level, however, with their ROM-Mark and BD+ uber-technology. It's a great read as there has been very little information about these technologies at this point. It's pretty scary stuff, to be honest.