[glhaynes]

Excellent answer, thanks, and I think my (also-hierarchically-inclined) gut agrees with your last paragraph: if you're gonna expose a complex filesystem to the user (and, for many usages, that's a good thing), hierarchical — with metadata/content indexing for fast querying — is probably the way to go. I'd like to hear of situations in this area where people think a tag system is/would be better than the hierarchy+index system, though.