If the tablet is nothing more than the ultimate personal media device, with an excellent and easy delivery method for publications (both for entertaiment and education), music, and video as well as a social networking/communications device, it will be a hit.
A handheld AppleTV plus eBook/magazines, plus iPhone like apps (including 3rd party devs) and they have a winner assuming it is easy to use. If they add iLife and/or iWork apps or video chat, even better. But even without those, it is enough to be a game changer. No product exists like that yet with an easy to use content delivery system. And there are several ways for many different companies to make money.