I find it unhandy that the "start date" and "end date" are not linked. Most tasks are just tasks in my mind. Projects would always have a "start date" and an "end date" but tasks by default in my mind should default to the same date. It would save SO many clicks if the default action was to mirror whatever I put in Start date into the End date field. Then the user COULD update the end date field to extend it if needed?
In the screenshot example below I didn't get to this task when I thought it would so now I have to 1) update Start date but now (as you can see) the END date is way BEFORE the start date. So I need to do the same three or 4 clicks on that field to update it. Action I would suggest is again to mirror Start date into the End date and again allow the user to extend end date if needed.