Vista Update: From preliminary testing, it looks like the UndoMinimizeALL method has actually taken on the function of, for lack of a better name, UndoLastWindowArrange :) -- the script equivalent of whatever 'Undo' command (if any) is available from the Taskbar context menu at any given time.
Note that 'Minimize All' is no longer a context menu option, but if you execute 'Minimize All' via the Winkey+M combination, 'Undo Minimize All' becomes available.