It would be great to have a visual of how a project played out by seeing the real start and end date of tasks. Not the start and due date but start and completion date. This would allow us to see when the tasks were started and when they were completed in a gantt chart form, regardless of due date.
What would be even better is if we can see a visual gantt chart of start, due and completion date. It would allow us to analyze where things took longer and report on delays, allowing us to learn from history.