It seems we all agree that libgnome/ui in their current form should be removed ASAP. But it seems people forget that we’ll still need a place for putting desktop policy APIs, and that makes libgnome/ui useful again. That is, instead of having lots of small libraries (gnome-menus, gnome-desktop, libpanel-applet, etc), it would make sense to me to have all those, desktop-related things, in one library that people use when they want their applications integrated into the GNOME desktop. Call it libgnome/ui or whatever, but you get the idea.
To start with, I’d mix gnome-menus and gnome-desktop, and then, if people agree, continue putting more stuff in those libraries. If done well, and only the right things are added, I think it would make sense a lot to have this GNOME Desktop integration library.