I'm currently trying to keep the app simple and clutter-free, so it's been a challenge not to pack it full of every feature that comes to mind. Sublists would definitely make it onto the feature-list; I think they're handy and my first prototype had infinite sublists. At this point, I'm not sure how I could integrate that in, but I'll keep it in mind. Thanks for your comment!

(Also, left/right arrows allow you to traverse days or months, and the down arrow focuses the add-task field.)