Well, I can't disagree with your anecdote regarding complaints (although I have owned both iPod and iPad since they were released and have never had a problem beyond the iTunes file transfer flow being awful), BUT the constraint to the Apple ecosystem and the iTunes flow are implementation details orthogonal to the actual hiding of the filesystem (i.e. it is easy to see how Apple could make file sharing easier without introducing the concept of a filesystem).

Maybe I was unclear in my earlier comment. The best way of implementing file handling is likely some full full-featured filesystem under the hood. My point is that this can be abstracted away to something more user friendly than a tree containing hundreds or thousands of folders and files. Transfer off a device obviously needs to be considered, but exposing a device (e.g a USB drive) as a hierarchical filesystem is usually unneccessary (and, IMO, counter productive from a usability standpoint).