@cedricmi: Completely understand about the reduced functionality, we made some choices about what was important in the app experience and we decided it was all about watching videos. We will be adding in more features as we move forward. As far as poor navigation, I don't agree personally, I find navigating in the app to be super easy... perhaps if you gave some examples of where you found it difficult that would help us to plan future changes.
As far as the general comment about reduced feature sets in other apps, I can't speak to the general case, but I can imagine that if you have been developing a web application like Amazon over many years, the depth of features would exceed a new UI that you just created. Also, just like we did, I expect that each company is trying to optimize for certain use cases for their Windows 8 app, instead of just handling everything. I think this is true for app development across multiple platforms, reducing the scope of a touch-focused app to make it easier and simpler to use. Over time I'm sure that some of these apps will get to parity with their existing web experiences.