I really miss Rdio! Just disagree on the performance a bit.
The UI was fluid, but their network performance would take a hit from how their API had been designed: every action on the app would trigger a large JSON payload download (and sometimes upload).
I was sad when I had to switch to Spotify. Rdio was clean. Even today I don't understand Spotify.
Rdio also had an amazing recommendation engine from Echo Nest. Even though that company got bought by Spotify it took them a long time after the acquisition before they had decent recommendations.
The UI was fluid, but their network performance would take a hit from how their API had been designed: every action on the app would trigger a large JSON payload download (and sometimes upload).
It definitely felt nicer than Spotify.