A couple of issues I'm seeing is when I click install, then I can't go back for several seconds to find more apps.
When I install an app and see it in list with other apps in store, there is no indication it is installed already.
Lastly, when I'm in an app, mainly Hulu at this point, there is absolutely no indication there is a menu above the screen. I'm guessing that where all Metro menus will be at? Even a tiny arrow would be helpful for new people.