1 and 2 are perfectly legit reasons to use Windows. 3, though seems weird. If you're installing something like Babun to make your windows machine act more like a nix machine, it seems reasonable to assume that a nix box would be better for your development needs, and that you have some other reason for using windows (like #1 or #2).
Well, if you're developing for Windows, or developing for the web and need to test Internet Explorer, or if you're either doing UI design or dealing with other people's UI designs and need access to Photoshop or Illustrator, or if you're using Visual Studio at least some of the time, or if you're working with a MySQL database and want to use something like SQLyog... there's lots of tools on Windows that can be useful for developers, and someone can very reasonably conclude that Windows (through something like this) offers better access to nix tools than nix offers to Windows tools via Wine.
Keep in mind that it's making the box act MORE like something else, but NOT less than what it currently is. People using cygwin and stuff like babun don't take away from windows, they add to what windows already provides, gaining a more diverse toolbox. On the flipside, adding things windows provides to *nix boxes to gain the same diversity in the toolbox would be very very hard.
