Impressive
Future additions could include filtering settings or a framework to allow users to develop their own niche to find music according to previous liked music. Of course it's not easy to make, at least an effective one, but I think it a good long-term goal.
Since you can save your favorites and go back to them later, maybe you could add on this and create playlists? Or at least be able to only play your favorites instead of just one song and going back to the random songs that is the radio.
I would imagine it being really nifty to be able to rate songs through the radio, but I would imagine that may go beyond what you can do because of the site. Still an idea nonetheless.
Also, be able to sort your favorites by ID, Name or Author. Maybe even history but allowing a time category so they can still look back to most recent, but if they think they remember the name and just want to search it.
There's a lot of room for this and I'm sure you're aware of that. Definitely something I look forward to seeing refinements from.