From the report summary:
Nearly all of the app stores more than doubled their number of available apps in 2011. Windows Phone 7 Marketplace showed the largest relative growth of all stores with more than 400% year-on-year growth. Combined, the seven major app stores now offer more than one million apps.
The Windows Phone 7 Marketplace is now the fourth largest app store when looking at the total number of available games, having surpassed both the Nokia Ovi Store and BlackBerry App World. The Amazon Appstore – larger than both the Nokia Ovi Store and BlackBerry App World as well in terms of available games – is now the fifth largest app store for games.
The catch now is to break away from the peloton of minor smartphone operating systems and close the game to iOS and Google, which are roughly four times larger. That's a huge goal, but if any mobile OS is going to manage it, on the strength of the Distimo report, it's going to be Windows Phone. The next step? Passing 50,000 apps, which should happen at some point in January.