Last Friday Spotify quietly updated its iPhone app with two changes to the app. One is one-tap log in to Facebook and 320kbps stream or sync quality. What really stuck in my mind when I saw the update was "320kbps".
You might think is not all that, but it really is. Listen to music in the Spotify app with low or high quality and then try the new quality option. Go to settings and go to each,"Sync" and "Stream", and select Extreme. The sync option will prompt you to re-sync back your playlists.
In the meantime, try listening a stream with the new quality and you will notice the difference.
The app is free and available in the App Store [iTunes Link]. A premium account is required.