In that field I'd say your problem isn't really about your app, it's just hard for people to get into the habit of using an app, so a high uninstall app once people give up should be expected.

One thing that I haven't seen yet (and I haven't tried yours) is a way to add a task through the notification screen. I don't want a widget on my screen, and having to flip to the right screen to load the app is enough work that I just don't do it.