He's right though - Panther isn't the same as a Media Library.
A media library, of course, works far better with MEDIA than it would with documents and applications, because every media file has the same attributes - an author, a title, a source, a year, a genre.
The glorious thing about departing from a heirarchical operating system comes from relocating files. Rather than remove a file from one location and place them back in another, you can simply alter a file's attributes so that it seems as though it exists in a new path.
You could also think of wonderful query-based goodness - sorting is awesome. Plus think of reports! You could instantly list the attributes of all the files in So and so location, or with so and so attributes, for analysing.
The advantages are amazing.
The OS would be far quicker too in every way, just because databases have ORDER.
It's a good system and I heartily agree Apple needs to incorporate a system like it.