Denis,
I was looking through your post about the beta release and saw the addition of the mini calendar for Quick Add. My first thought was that it was unnecessary, but then I realized that the screen space there was unused anyway, so adding in a mini calendar isn't obstructing any other interface elements. It's also nice to have the ability to quickly set a due date as you add a task.
The only thoughts I have are these:
1) What happens if my task is due later than the dates displayed on the mini calendar? What if I needed to set the date to April 15 when the calendar only goes to February 27?
2) Can the calendar grid better fill the space between the task title and the keypad? Nearly 1/3 of the empty space is unused. Perhaps you could expand the grid height slightly to make the dates easier to select, and if there's still room, add a way to toggle between months in the calendar.
Personally, I rarely set due dates on my task items, but I realize many users do. So I would be comfortable if this was available only in the Pro version.
Hope that helps!