Someone edits a page, saves it and choose not to publish it. Then when someone else tries to edit the same page, it would be very usefull to get a message that the page is in draftmode by someone else and that the page can't be edited until that person decides to publish or cancel the draft.
It would be even nicer if a mail is sent to the other person with a link to the page and a message that user want's to edit the page.
An administrator can select to publish or cancel the draft made by others.