GNOME Shell (both master and the overview-relayout branch) present the list of launchable applications to us as a large, non-hierarchical, immediately searchable list. We can hit the logo key and start typing a few letters and immediately find what we're looking for. KDE has it. Windows Vista and 7 have it. OS X has it (via Spotlight). And now we have it.
On Debian this is a problem because menu and menu-xdg convert an ancient, Debian, unified menu system that predates the existence of the cross-desktop XDG menu specs in to XDG menus and stores them in
/var/lib/menu-xdg duplicating everything that's already in the standard
/usr/share/applications. This wasn't really a problem because all the duplication was crammed in to an easily avoidable "Debian" menu. The idea was that you'd get the same Debian menu in all desktops. Unfortunately, this isn't getting killed off fast enough. However, we can change it for our own systems.
sudo update-menus --remove
sudo apt-get purge menu
The first step is required because
/var/lib/menu-xdg is not considered configuration and therefore the contents of this directory are not removed on package removal. It is necessary to the remove the menu package to prevent package installation from triggering the recreation of these menus via the dpkg triggers mechanism.