Don't forget the only thing that would really change is that there would be non-games on the Steam store.

The entire "product" already exists, they just need to bring non-game titles to Steam. (and from the sound of that announcement it seems they already have something lines up)

Steam will work on Windows 7 and XP unlike the Windows 8 app store. It also runs on OSX and soon Linux. What exactly is Microsoft supposed to do about it?