Though some time ago I had discovered Pandora, I never really liked it, because it
never rarely played music I wanted to hear. However, eventually a friend explained to me that it takes thumbing many songs before it knows what you want to hear. I now hear almost no music I don't like. For example, I have been listening to my classical quick mix for 3 hours straight now, and I have only thumbed down two songs.
Try it. It may take some time, but eventually it will be practically perfect.