I'm not sure if this is intended or not, but if you edit a sync'ed playlist on the mobile app (i.e. add a song or remove a song), those edits don't sync to the PC side. Not only that, but it seems like the sync doesn't even touch the playlists, so the playlists get out of sync.
In case you don't see why anyone would care, my motivation for this is as follows - I wanted to have a "Remove from phone" playlist that I could quickly add songs to, so that the next time I sync I can see which songs to remove from the (other) sync'ed playlist. I'd welcome any other approaches to this

Thanks again,
Al