These days the talk of App Stores is all about Apple for its iPhone and iPad, as well as the Android Marketplace for those running the Google Mobile OS. RIM, Palm and Nokia are also players in the apps market, so it's definitely the new way to distribute software.
Microsoft could be planning the same sort of thing, but for the full-blown desktop OS Windows 8. According to the leaked slides, Microsoft wants to make it easy for users "getting applications they want, that they can feel confident in, that they can use on any Windows 8 device."
Windows 8 won't be confined just to the desktop and laptop space; Microsoft is aiming to make the operating system suitable for slates, laptops and all-in-ones. While Windows 7 already accomplishes this, the addition of the App Store makes it more crucial for Microsoft to ably handle software offerings consistently across the various form factors.