Spotify employee Bob Jelica (@b0bben on Twitter) just posted a video of a Sailfish Spotify client which was developed by him and Pär Bohrarper (@rogueops) as a Hackday project. The user interface shown in the video really looks great and could be an example for other, future Sailfish OS apps.
It's not sure though if this app gets ever released - follow Bob Jelica if you want to get the latest update about the project.
But who knows: Spotify for Linux is also labeled as a project and is not officially supported as well. Yet it is a perfectly working client which keeps up with Windows and Mac OSX versions.
The official Android application works also well on Sailfish OS and don't forget about CuteSpotify - a wonderful native Spotify client available here or via Warehouse app.
Hackday project by me and @rogueops : Spotify on Sailfish https://t.co/0YJKx0fWZs #jolla /cc @zzste @MarcDillonDotFi :)
— Bob Jelica (@b0bben) July 17, 2014