Maybe I broke something, but the expected behavior is for Maemo Mapper to bring up the "Manage Repositories" dialog automatically upon first start. That's where you specify the Map Cache DB location. It's possible that I broke the "first start" detection code....

Of course, I'm sure most people just breeze right through that dialog. They probably also press "Cancel" when Maemo Mapper suggests that you read the "Quick Start" help document....