Feedback on my project
pedalpete: I've had some experience in this space, and good on you for tackling a very challenging issue.I really like how you've done your interface, the ability to add and filter by a fairly easily understood group of labels.Unfortunately, you still have a lot of work to do on the quality of playlists being created. 
I started with funk/slow temp and got back Neil Young and the Beach Boys. I kept going and added 'bass', and I have a very twangy harmonica filled blue grassish track by "the trouser legs of time".The best I have seen to date is http://theperceptron.com/ which was written by a girl from the UK (I believe a CS student as well).
Looks like they opensourced their technology too, check it out (their site used to play the tracks, but apparently it doesn't anymore) :(http://theperceptron.com/blog