On the iPhone, swiping allows to go from todo view to calendar views : month, day, list.
I most use the calendar list view and todo : this makes me swiping through all views.
The easy to implement idea, is just to make it round :
- swiping right on the list calendar brings to the todo
- swiping left on the todo brings back to the list calendar
Another wish is to have a button to go back directly to level 0 (I use 4 levels of categories).
Also, if one day you get direct access to iPhone's Calendar, please don't merge it with your calendar except the user wants that : I have two different jobs, and i am very happy to use ToDo+Cal+Sync for one where it is appropriate, and iPhone's calendar for the other one. I certainly don't want both of them in the same calendar.