... i hear more details and feel more surrounded by the music than with my D2000's or ESW9's. the ESW9's are pretty detailed and transparent too, but the HD650's feel a bit more laid back, cleaner and relaxing to my ears.
i listen to a lot of electronica where the - tat tsst tsst tat - sounds can sometimes produce piercing sibilance. happy to say that while these sounds are still as clear and detailed with the hd650's, they don't cause fatigue...
Of course, they may brighten up with burn in.