Pandora, your automated DJ

A friend of mine (Adam, who never updates his blog) told me about this music service, Pandora by the Music Genome Project. You put in the bands you like and it plays songs from that band and other bands that it thinks you will also like. You can create multiple 'channels' of music.. ie; A tragically hip/metallica channel and a eminem/queen channel (not sure what the later would produce).