At its Stream event, Spotify introduced a new feature called Smart Shuffle. If you have a small playlist with songs that you really love but need some new blood in the list, you can simply press the button. Then you’ll get some new music that should fit the other songs already in the list. If you like a song, you can add it permanently, otherwise songs will disappear when you turn off the feature. If you turn it on again, you’ll get a whole new set of song suggestions.
It’s nice when you want some new blood in your favorite playlist, simple as that.