Depends on how much $ you're making from it and what sort of growth you think you can achieve.
I checked out the app and it looks very nice. I will be buying soon.
I checked out the app and it looks very nice. I will be buying soon.
Ideally I'd like to see it become a Web+Device synced version of Things that actually exists.
It sounds like a large project compared to just steadily polishing the app itself and starting a second app on the side, or even as your new main project.
An added benefit in starting work on a second app is diversification, different target audience, different appspace. You say building a good app is hard, but so is building a good web offering.