According to figures published by app market analyst Distimio, there are already more than 20,000 applications in the Windows Store compared with 13,000 in the Mac App Store.
No other app store has achieved such a large number of applications in one month, officials said.
Daily download volumes for the 300 most popular applications are three times higher at the Windows Store than the Mac App store, Distimo's report noted.
At least two matters should be considered. One is that as the Windows Store caters for desktops and tablets it might more properly be compared with the sum of Apple's app stores for Mac and iOS.
In that case the number of apps in Microsoft's store is a small fraction of those in Apple's.
Then again, the Windows Phone 8 Marketplace wasn't included in Distimo's analysis, so arguably no meaningful comparison of app numbers can be made.
The other is that the newness of the Windows Store and of the Surface means there could be a novelty factor at work.
Compared with other stores, the Windows Store has an unusually high proportion of free content at 86%.
That's practically the inverse of the Mac App Store, where 84% of apps are paid. Google Play is 35% paid.
But Distimo noted "it could very well be that the Windows Store soon will overtake the Apple Mac App Store for paid downloads as well."
And who are the top publishers in the Windows Store? No surprises here: Microsoft, Rovio (the Angry Birds company) and Google (largely on the back of the Google Search app).
You can find Distimo's app charts here.