>But the average, non tech savy users have a very hard time understanding hierarchies and therefore tree controls

Oh, that sounds very much like BS. "non tech saavy" users have been using hierarchies in computers since before Windows 95 (considering people that used MS-DOS as 'tech saavy' users). DOS/Windows folders were presented in a structure; File Explorer presented stuff in a structure manner. Hell, the "my documents" folder was structured... and even Gnome (the epithome of doing simple interfaces) presents folders in a structure manner.