>It's difficult to think of a reason why anyone would go for this or why this even exists.
I don't think MS expect *nix users to come flocking. They are trying to staunch the flow of Windows users who need *nix tools from jumping to a proper *nix OS.
I think the idea is that you run your OS-independent business-logic cloudy app on a cheaper version of Windows.
If you need IIS, you can jolly well carry on paying for Windows as usual.