Today the Spotify app on Windows Phone 8 and 8.1 was updated to version 4.0 and made it possible for Windows Phone users to finally listen to music on Spotify without a Premium account. The update basically brings the app on par with Spotify’s offerings on iOS and Android.
After playing a bit around with it I can safely say that it works the way you would expect. Here are some screenshots from it:
If you haven’t updated already, head into the Windows Phone Store and grab it