To continue J515OP's train of thought. By creating a correctly written app for Windows 8 (i.e. Metro or whatever Microsoft is calling it now) it should be extremely easy to port it to all versions of Windows 8 (Pro, RT and Windows Phone 8). That's massive. If they really pull it off it'll push Microsoft over the top. Before it's done I'll have a Lumia 920 running Windows Phone 8 (got a Lumia 900 now), a Surface RT and most of my "old" computers will be running Windows 8 Pro. If I can buy one app and use it on all of my devices, Oh Helios, I'll have a nerdgasm!
-joe-