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.