When you talk about an App Store, right now that usually points to something Apple-related. Apple would love the trademark to that name, but Amazon's fighting that with its own "Appstore" and so is Microsoft – possibly because it will have its own application store soon too.
A leaked screenshot published on ZDNet points to what looks like a Windows application called "Windows App Store." This new feature is believed to be in the works for Windows 8, but the screenshot appears as Windows 7 in theme. If Microsoft were to launch an App Store that will be integrated with Windows 8, it's likely that it will also offer it as an add-on to the growing Windows 7 base.
Over 212,000 for Windows
Over 31,000 for Mac
Over 426,000 for Mobile
It's called www.download.com and it's part of Cnet and it's been going since 1996, it has free software, shareware, trialware and purchase.
Why the hell would you go anywhere else?