I own them (and have owned each of the models as they've progressed). Here's the appreciation thread. Personally, they get more head time than my HD800 and HE-6 combined. Living with a noisy dog, loud air conditioner and other background noises, it's much easier to just grab the closed cans. I will say that they isolate more that the old Denon D2/5/7K line of closed cans. The do have a slight venting, but they're really difficult to hear anything from the outside.
Oh, and I think the sound pretty good.
Thanks! I'll check out the thread. Srajan seemed to like them. It's always useful to have a pr of closed cans around.