Nice start - I think there is ultimately some value in this approach, but currently seems quite limited in its functionality, for example I can only choose one song? This results in a very large set of results to wade through, many of which will not be helpful or relevant.

Personally I'd get far more value if I could chuck in 3-4 favourite songs and see which playlists contains all of them (or order by greatest number of matches first); this would allow me to more accurately match my tastes to discover a potentially new bunch of other songs I might like.

If there is a way to match against more songs, apologies! The post title implies there is, but the site seems to suggest it's limited to one song.