This would be awesome. The one problem I've had with Spotify's radio service is only being able to pick up on genres and such. Many times I might like only 1 or 2 bands from a more obscure genre, but spotify radio does not understand this no matter how many songs I downvote.

In fact, my "starred" playlist radio is currently stuck on some kind of 80s metal thing. I have no idea how it got that way, but it refuses to play anything but metal, when that's not really what I like. If I make a copy of my starred playlist and make a radio from the new playlist, it reflects the actual songs at hand..

There's also the matter of unique bands that while fitting into a very wide genre, don't really fit into any widely known sub-genre. Meaning radio for the band is almost useless in many cases. There is the "related bands" bit which helps it a bit, but this only works with popular bands and still is very mismatched often times