To cope with fragmentation of their Android OS, Google has revealed on the Android Developers Blog they are now allowing multiple APK support. Historically, Google only allowed one APK file that would in some cases work on only a number of phones.
With multiple APKs, Developers can now build their apps for different screen sizes, processors, and other hardware capabilities. When a user downloads an app from the Market, they will be automatically assigned the APK that best matches their phone. On the Market all of the versions of the app will be aggregated into one for ratings, reviews, and listing. Google notes what devs need to know:
To support this new capability, we’ve updated the Developer Console to include controls for uploading and managing APKs in a product listing — we encourage you to take a look. If you’d like to learn more about how multiple APK support works, please read the developer documentation. As always, please feel free to give us feedback on the feature through the Market Help Center.