Love the idea, although I feel like the playlists generated aren't... great. For me it was grouping things in a pretty odd way that didn't make sense (e.g. Bob Marley under a "punk" playlist)
yeah, exactly. Artists genres are weird and the algorithm uses a weighted system to determine the clusters. But you need to try a couple of different options to get what you want.
MusicBrainz and LastFM have much better genre information and on a track level, IIRC. Their APIs are free, I think. You could use them to look up genres.