I was updating iPhone apps the other day and noticed the difference in how app developers describe their updates. In almost any app developed by a startup or internet company, app updates often provide detailed descriptions of the updates made to their application, whether they're new features or just bug fixes. Example:
WOW! Thanks E*Trade! I can't wait to download your app update full of maintenance stuff!
The point is, people like to know what's going on with their devices. Even if you're just fixing stuff, let people know! If you're going to require a user to update your app, you should at least give them the courtesy of letting them know why they're going out of their way for you.