Three things to think about for whether or not a gadget, app, or any other product is worth your continued investment of use and money.
Good list, however I would add another point:
- If you don’t like to use it would it be even worse if you wouldn’t use it?
This point is, for example, for finance applications. Everybody hates dealing with financing and no app can make that fun again, but at least they can make it less worse.