well, super congrats to jonbob for finally sneaking his menu stuff into drupal cvs. i've just played with it for a bit (briefly) and it's very flexible. i like it a lot. it not only lets you fiddle with the default 'navigation' menu, but allows you to define completely custom menus.
i'm gonna keep playing with it, but it should be able to easily do custom layouts for completely admin-configurable menus and navigation (and sitemaps, etc)! :)