[pizzaburger]

Sure it's gaming-specific, but more prior art: http://steampowered.com

[mishmash]

It's one click and a password to buy from the Mac App Store whereas Steam takes five clicks and no password (if you have it set to remember).

Apple's store is no revolution in my book, far from it, but at least they put that Amazon One-click patent to good use and made the process easy.