I believe it works with PlayTo. If you have a Windows 7 PC, at least Windows Media Player should have a "play in device" (rough translation, I have Media Player in my native language) that should show Xbox One if it's connected. With Win 8, when you want
to PlayTo something, you should be able to get the Charms-bar from the right, then devices and it should have Play To.
Media Center is not supported per se like 360 was as an extender, but indeed PlayTo should work when you figure out how to use it. I can't give very good instructions cos I don't have Xbox One myself yet.
You can't at this time. Support for external USB devices is coming after launch, but what you are trying is impossible for now. You should be able to stream them from your PC if you have a Win 7 or Win 8 computer.