As the dead user below mentions, one of the issue is that there are sometimes no indication at all on screen on what you can do and cannot do. The problem with such an interface is that it is not "affordable" in the design meaning of the world. It does not provide clues as to what to do next. That is precisely why you had so many videos on youtube showing people testing W8 and not able to find how to shut down their computer. There is no way you can find out unless you RTFM. At least the start button was a way to centralize things. With metro, there is no center anymore and it looks very confusing.