Well, looks like there is a pretty big issue related to "adding all songs in a playlist to a user's library". I created playlists on my iPad, and it added all these songs to my library on my iPad. But it didn't add them to the library on my iPhone. So I can see the playlists there. But I can only see the songs in the playlists that were already in my library. All other songs don't appear in the playlist when I view it on my iPhone, because they were not added to my iPhone library. So one playlist with 50 songs that I created on the iPad is completely empty on the iPhone.
Well, that kinda sucks.
Well, that kinda sucks.