The Xbox secret? Simplicity. Each video is only a few button presses away, and the console is (usually) already connected to the TV. For most users, Amazon is confined to a PC monitor, likely stashed on a desk, tucked away in the corner of the house; and getting content from Unbox to the TV is a tedious process.
So has Microsoft nailed it? Is Xbox 360 the frontrunner of the digital distribution era -- even with a 20 GB hard drive and limited studio support?