You must have Web interface to succeed!
I’ve checked many to-do apps so far, but I still haven’t found the perfect one. The last one I’ve been using was Any.do. And it was close to perfection. It had nice UI, almost flawless functionality and felt nice.
As for functionality. Almost everything was alright, but adding items to lists sucked. I’ve had list called shopping, so I’ve clicked plus near it and added the item to it. The obvious consequence to me would be that if I add next item it would be placed in same list.