Rdio. Music Streaming service. Not sure what happened after they closed up shop but the UI was beautiful and they had great performance.
Closed and recovered as OSS by the former dev of the company as « OpenWhyd », and still accessible for free on a server, but he’s getting tired.
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.
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.
Pros: Snappier to use, faster to open, never see the "Updating spotify" interstitial.
Cons: Spotify quits when I cmd-q Chrome, completely different UI layout to the thick client, doesn't understand the OS-level media control keys.