Passing such a significant milestone just four months after launching Windows 8 is a good start. By comparison the Mac Store has roughly 15,000 apps. It is worth noting that developers still have yet to fully embrace the platform and deliver top notch apps across all categories. The Windows Store is shared by Windows 8 & Windows RT.
It is worth noting that app submissions to the Windows Store has slowed each month since launch. Still if the ramp up of official and fantastic apps landing on Windows Phone 8 it isn’t a hard stretch to think that the larger Windows 8 platform should see a significant increase.