Google's Android Market has released a new feature for developers called Application Statistics. As the name implies, developers can now see detailed data about their applications. More importantly, they can see data about who is using their applications, and how.
On the Market Developer Console dashboard, you can see an overview of app performance -- each app’s active installation trend over time, as well as its distribution across key dimensions such as Android platform versions, devices, user countries and user languages. Also, you can compare your app's statistics with every other app's installation statistics across the market.
The key advantage here is optimization -- the more you know about your audience the better you can tailor your apps to them, as well as your marketing messaging.