A nice feature for the menu system would be the ability to drag/drop dynamic blocks. For example, I want to have the menu automatically put all sub pages of a specific page into the menu as a drop down under that page. So you could add a new dynamic item to a menu, that menu item would give you various options like:
"All sub pages of [select page]"
"All posts in [category]"
"All posts in [custom post type]"
"All posts in [custom post type] with [custom taxonomy]"
So instead of adding the content, then adding that individual item to the menu as well it could be done automatically.