One of the things that I really enjoy is the sorting functionality. The interface for sorting is among the best I have ever used in a task manager.
The web app remembers the sort order based on the view you are in. Due Date / Context / Search etc
This is incredibly powerful, however the IOS app doesn't do this. When you adjust your sort order it will follow each view. I end up changing the sort order of the tasks for each view that I enter.