I just received these last week and I'm loving them so far. I've only got about 10 hours on them so far, and was wondering what the optimal burn-in time is for this particular pair of phones, as I've heard differing things for the 580/600/650 series with regard to burn-in. As I said, I'm pretty impressed with the sound right now-- alot thicker sounding than the Grados I've been using. It's weird being able to hear alot of detail without the treble being too bright. I'm used to associating more treble with more detail, and with the 580's, that just doesn't seem to be the case-- they're pretty detailed despite having a much warmer sound signature than the Grados.

I'm also burning in a Go-Vibe amp right now along with the HD580's... the first time through it only got about 15 (versus the optimal 50) hours of battery life with the AD8066 opamp (supposed to be similar in power requirements to the AD8620), so I'm assuming capacitors and what not need to reach their optimal efficiency (and cheapie Eveready batteries don't help!)