Nothing more important than retention. Even more important than getting the users in the first place.
Nice article on how to keep them in your app. 6 tips:
- Performance - work smoothly, run quickly.
- Design - easy to use, easy to understand.
- Same experience on all devices.
- Usage - don't drain the battery, don't get to many permossions.
- Murphy's law - make sure all your funcionalities are working!
- Play nice with other apps - refer users to them, work with them.
Overall, this should give any developer a general idea how his app should behave, no matter the type of app it is.