It also does it across devices! I have a crappy old smartphone w/o a sim card that I use for running, and have a running playlist pinned to it.
I can be listening at work, add a song to the playlist, and then back at home the device automatically downloads the new song over wifi for when I go running. (I'm sure spotify does this too)
I can be listening at work, add a song to the playlist, and then back at home the device automatically downloads the new song over wifi for when I go running. (I'm sure spotify does this too)