Looks like OS X and Linux have nothing to worry about here. It's the Microsoft Bob idea wheeled out again with a trendy minimalist feel instead of a dog.
Windows users will not switch to Linux (but it's the year of Linux on the desktop!) because of the usual issues, but serious (non-VS-using) developers will never use Windows either. As for OSX, Apple hipsters aren't going to spontaneously start using Windows, and Windows users aren't going to start spending 2x as much on their computers any time soon.