I often use the To Do checkbox when making a list of action items during meetings. It would be excellent if when I clicked the To Do checkbox to mark the action items as completed that two things occurred:
1. Display a date & time stamp when the box was checked and lock the box against accidentally unchecking, but make it easy to uncheck if necessary. Suggest a double click to uncheck.
2. Provide a way to enter a comment about the item being checked off. For instance, if I followed up with someone to get an answer to a questions for the next meeting, it would be great if I could check the action item as complete and add a comment with the answer to the question. This could be done by either automatically inserting a comment box under the To Do item right where it exists on the page or by creating a table/log on a separate page that you're automatically linked to when you check the checkbox.