Access metadata when listing menu (nav menus in WP3)

Sometimes I’d like to be benefit from the sorting in the menu editor for my custom post types. The problem occurs on the frontend (or where I choose to list my post type), if I’d like to have some metadata, for eg. extension, next to it and change the markup depending on that metadata.

Is there anyway to access the items, I’m thinking the ‘wp_nav_menu_items’-filter, but it seems like I can’t use it that way.

Thanks in advance
/ Anders