Sometimes I've completed a portion of a task, or am waiting for someone else to complete their portion after I've started working on it. In the calendar task pane (on the left with my google calendar, for example) my RTM tasks have three options in the dropdown: Complete, Postpone, or Edit.
Since many of my tasks stretch over several days, it will be helpful to see which have been started and are waiting further action. Adding an "In progress" indicator to a task would be helpful. (In a Franklin Covey planner, for example, you would put a dot next to items that are in progress and that carry over to a future date.)