The first things that comes to mind:
- Browse by label (additionally sort by most recent releases): I know it's not a mainstream thing, but labels, particularly smaller ones, are very good curators and a great indicator for worthwhile music. For the music I enjoy it's absolutely necessary to keep up with a label's recent releases.
- A great community that had tools to discuss music and releases:
Being able to comment on albums, playlists and other items seems like a very obvious feature to me. And it was a powerful one on rdio - You'd often see familiar faces in the comment section of an album and start interesting discussions. This isn't possible on Spotify at all.
Furthermore I could see what's popular among my friends (and not just in general!) on a single "Heavy Rotation" page - if you carefully select who to follow, this is invaluable.
I have a similar follower count on Spotify as I did on rdio, but no meaningful way to interact with them - there's an activity feed where I can share discoveries with everyone, but it's the saddest thing I've ever seen in social networks: It's a one-way feature to shout recommendations at everyone but there's no way for others to get back to me and add their feedback. I might as well talk to myself. If you enjoy being a curator and recommending things to others Spotify is close to useless.
- A working queue:
This is just horrible. It's not obvious at all how the queuing system works in Spotify. Apparently it's tied to whatever client you're currently use. Listening on mobile? Better prepared to see a very different queue once you switch over to the desktop. In rdio the queue was basically a persistent "Listen later..." playlist - it could differentiate between single songs, full albums and palylists - if you had an album and a playlist queued it would show two items which you could drag and drop in order to move up or down. Beautiful. Enter Spotify: Imagine you're listening to an album and you'd like to add a second album to be played after the current one. Instead Spotify will start playing the second album immediately after the current SONG thereby interrupting the current album. By the way, the option to start that confusing process is called "Add to queue", not "Play next" which doesn't exist. Horrible. On iOS you can't change the order of the current queue either - you can't even jump from the current track to item #27 as the only way to navigate the queue on iOS is to skip track by track. It basically means that you'll never use the queue for anything and just create your own "Play later" playlists.
I get the feeling that Spotify is for people who don't want to deal with music. Start the app, hit play on a Spotify-provided playlist with a hip background cover and mildly interesting name and be done with it. That person is not me. However I can see why it was appearing to the masses. The sad thing is that rdio could do all these simple things and be used in similar fashion to Spotify and its playlist-centric approach too - it just offered all those additional features on top and still lost.