For months now, longer than I can remember really, I've had my empeg playing my entire Rock super-genre playlist on random; 3000+ songs. Now that's a mix of pop, punk, folk, classic rock, hard rock, indie, etc.

The shuffle mode has an uncanny tendency to fill my commute with tracks that go well together. It's like having a good DJ in my dash.

Now if only I had time/ability to create attribute tagging/querying for no-guesswork perfect mood mixes...