Also, assuming that amazon will make an app for the new Apple TV (which they seem to have done for all iOS so far) the new apple tv will play EVERYTHING - Plex, Amazon, Netflix etc, and iTunes content.
I know it's apples fault for not making iTunes-playing apps for other devices, but that doesn't change the fact that with AppleTV I only need one device, versus every other solution. It's just plain more convenient. Of course, this only applies if you are in the apple ecosystem to begin with, which is maybe not who these are aimed at...