An interesting infographics was published on the WP7 developer blog.
The most interesgint points that we saw are that 56% of the users can purchase apps via carrier billing which is amazing number for a young platform. Android did not have carrier billing for at least a year into its existence if not two years. Which was a significant barrier for selling paid apps since billing mechanism was not oiled like on Apple's iOS platform where all the users have iTunes setup with their billing information.
Surprising enough the Games category is not as huge as we'd expect it to be. Taking a little smaller percentage than the Entertainment apps in the app to category distribution. But in the paid apps category Games are far ahead of any other category in purchases which of course should not be surprising, although this trend is not so prominent on other platforms.
Overall it seems pretty good info and quite useful for developers. Enjoy!