they work great with Clementine, too, which is cross-platform. and with a SD/flash adapter and Rockbox, the older models can still be capable little devices today. rockbox, at least, does start to chug a little with dynamic playlists over several thousand songs, though...
honestly, the only thing the classics are missing for me is a physical off/reset switch. sometimes i've needed to reboot to apply a mod or something, or the little thing freezes, and if the hidden key combos don't work for whatever reason, then i have to spudge the dang thing open and reseat the battery's ribbon cable
It's funny that the author didn't think to try Music.app instead of doinking about in Finder. I just did this a couple of weeks ago with my own iPod Classic: Music supports iPod sync just fine. (Yes, still!)