The iPad app could use some extra functionality.
I'll try to make a list of what could be added for better usability.
FEAT: sorting in playlists (default, track name, artist name)
FEAT: deleting song from playlist, just by swiping that song (or in the submenu that opens but don't let me scroll all the way back to the top)
FEAT: show star icon by default, not only when the submenu opens (like Android)
FEAT: iPad has no library?
FEAT: filter/search bar for playlists
FEAT: show list of artists in a playlist to use as a quick filter
FEAT: if song is in a playlist, color the + sign, same as done with star for favorite items
FEAT: if you added a song to a wrong playlist, use the + also to delete it from that playlist again
FEAT: show songs in favorites but not on any playlist (or does library do this?)
BUG: If you scroll manually on artist level, you will find albums not shown at "All albums"
It's sadly very hard for us to mark this thread as "implemented" or not, as there are quite a lot of ideas here. We've created some Idea Submission Guidelines for people to have a read when posting up ideas for Spotify.
For example, if we include an library and some playlist sorting options, but want to look into the rest later on, it's still impossible for us to say that we've actually done something about this Idea. For the time being, I'm moving this over to the iOS board for more consideration and discussion on these features.