Back when Pandora first launched and was available in Ireland, I remember that it required you to put in an artist/song you liked and it would seek out similar music based on that artist/song's features - this approach seems to be slightly different in that you don't need to know any artists to start off with.

Though, now that I think about it, I'm probably more concerned with musical genre than a lot of casual listeners, and perhaps everyone is not aware of what the genre they are seeking is called. So this may only be of benefit to a minority of people.