Number of the published apps
According to the number of individual app pages on apps.microsoft.com, almost 30000 apps are currently listed (December 12) on the Store. Some of this apps are published just for selected markets and as a result the effective number of the apps available for the users may vary from country to country.
The following charts are based on the US market numbers.
App categories
While it was expected to see games and entertainment apps among the leaders of this chart, a large amount of educational apps is a surprise.