Within most workflow activities there is the option to define due dates. These are based either off the start of the activity or the start of the workflow. Why can't these be based off the Due Date field designated at the start of the process? For short workflows it's often desirable to set based on this date rather than some arbitrary amount of days/hours/minutes.
I'm sure there are possible work arounds using code but it seems reasonable enough to be able to use the designated date.