Another note re: burn-in.
Yesterday I dropped by the Magnolia room on my way home. I had some time so I decided to give the Momentums another listen. Also spent some time with the H6. Then, for comparison purposes, I plugged my iPod into the P7 they had on display. It was like being hit over the head with an aluminum baseball bat! They sounded much harsher than the ones I've put about 200 hours into. When I got home I plugged my P7s into the same source and played the same songs. Much mellower sounding.
I've also found that after long sessions my earlobes do start feeling some compression.
Makes me wonder if maybe B&W will eventually offer some alternative ear pads for these...