Show part of the next month in the date picker
The new date picker is a significant improvement over the old widget, especially on Ubuntu, but could be made easier to use.
The most common use I have for changing the date for a task is procrastination--moving the date a couple of days into the future. At the end of the month this gets harder, a few days in the future is the next month.
It would be nice if Task Coach date picker took the approach of other electronic calendar selectors I've seen and showed a few days of the next month and allowed them to be selected. For a "few days" I suggest filling out the current row on the calendar with the start of the next month, and adding the first week of the next month if there are no spaces in the current week.
(Often the last days of the previous month are shown, but I find that less useful for task date manipulation.)