It depends on the application's target device
I like the idea of being able to develop native metro apps on a desktop PC then install them on mobile and tablet devices. I also like being able to write desktop applications that run on desktop and notebook computers. The desktop metaphor does not work well on small screens. The Metro interface does not work well on large screens. Providing that Win 8 eventually makes using desktop applications easy then it gives you the best of both worlds.
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