That's brilliant. I'd never noticed that about Mac OS submenus (although I definitely noticed how arduous it was to navigate Windows submenus).

I do have one outstanding gripe about Mac OS menus, though, which is that if you misclick on some non-reactive part of the menu (a greyed-out option or divider line), it simply closes the menu. I can't think of any reason why this would be better behavior than leaving the menu open, since at least 90% of the time my intent was to actually click on something that would respond.