I'm sort of torn about Listen. For US$0.99, this iOS utility from Daft Logic Studio offers a lively and engaging music interface. At the same time, most people experience audio with their ears, and not their eyes and fingers.
The app is well made, with lots of features and special effects -- as you can see in the video that follows. It was nice to use even if I think a few of the effects are slightly over the top, such as the ripples on play/pause.
To sum up Listen, it offers a suite of custom gestures for controlling your music, social-network integration and caffeinated auto-lock override, so your phone stays awake if you so desire.
As far as apps go, this may be a "love it or leave it" title. Me? I like it. I appreciate the design effort that went into its GUI. It showcases lots of clever ideas like dragging the playing music to the feature you want to invoke.
Will it be a successful long-term app on my phone? That, I'm less sure of, but I give snaps to the developers for their creativity and I look forward to giving it a good trial run over time.