Columns Sort by Click at Top of Column
this will enable, for example, a "Due Date" column to sort and show what Tasks might be due. OR would enable the creation of a GTD context-like column where all like contexts could be sorted for review and execution, etc, etc.
Mike Shinn commented
Should be able to sort under selected parent , level of indentation or whole document. Sorting should not affect hierarchy, but offer a different view. I think this would be a powerful tool.