A lot of what has changed is behind the scenes. New security models, new APIs, etc. "Aero" is the most obvious change from a user's perspective, though it is mostly about cosmetics. 64bit support has been around in Windows for quite a while now, both in specialised (Itanium) and consumer-level products (XP64 and 2003 Server x64), so you could hardly say Vista will "introduce" 64 Bit computing.
Vista will be more of a pardigm shift that is necessary for future change than a breathtaking change in and of itself. MS doesn't need to convice the consumer to upgrade - they only need to have OEMs package it with new systems. Business can be forced to change by cutting support for leagcy products (or making them pay for it).