Guys, it isn't the OS, it is the APPS....
If the OS runs the program you want or enables you to do what you want, then that is the OS you need.
Be it a game, like Angry Birds for instance, a DVD creator (yes, each OS has one, but some work better than others, or you own one), or an in-house built app, that will determine your choice of OS.
I don't know of anyone that buys an OS to just run it? Can't do anything with an OS, other than what is built-in. Want only e-mail, browsing, enter a document, they all do that... it is the 'extra' needs that determine what you use.
Thinking of e-mail, even the platform could determine your choice of because you have to enter data to respond to e-mails. Tablet's just don't cut it with on-screen keyboards. Ultra-books might, but the keyboard could be 'small'. Same for Netbooks. Laptops and Desktops are far better for this task for instance.