FYI, this is not true for Windows RT (the ARM version). That version will only support applications purchased through MS's store. Given that MS is clearly pushing for Metro to be the future of Windows, I think this is somewhat concerning.
On the other hand, Windows on ARM is an extension of the Windows franchise in the same way that WP7 with it's app store is. In a sense it is like talking about the iPad when discussion the Mac App store...or would be if iOS applications ran on the Mac.
Metro is a future of Windows, just as Server Console mode is (though admittedly on a potentially different scale).
