Is Microsoft leading the way to a unified platform?

Isn’t it a pain when you have to buy or download an app 2 or 3 times if you want the different versions created for your PC, your tablet and your mobile device? Isn’t it a much BIGGER pain to be the one that has to develop or test 3 separate versions of that application?
Microsoft thinks so, and they may be just the first platform to dive into the idea of unifying their...