With the various reviews of the Apple TV device I think that people, including Apple, have missed the point. This shouldn't be a device via which you stream and buy content it should simply be considered as a dongle, which in future can be integrated into the TV, car or what ever to stream content from a portable device. $99 is quite a bit for a dongle but Apple have actually over speced the Apple TV device so it will stand alone, the smart move in future will be that it is simply an extension to TVs in the way they have iPod connectivity today. The storage is on your PC, Mac, iPod, iPhone or iPad and then you simply stream to the various different displays that are available.
So you carry around your movies, in conjunction with your Apple cloud service and thus it is all on demand as you travel around your life. Get in the car and the kids can get it, get home and you can use the TV. Go to a friends house and it is all sorted.
Seriously is it that hard to spot? Apple TV isn't a product its just a dongle that can be integrated into TVs based on the iPod, iPhone, iPad dominance. Airplay is the real thing, Apple aren't aiming at the set top box market or even the movie rental market, they want the last metre between you and the display.