My order from Musician's Friend arrived today; the main item was the Extrene Isolation headphones. (Browncoats will appreciate the URL: SerenityHeadphones.com. Unfortunately, it immediately redirects to ExtreneHeadphones.com, but it's the thought that counts.)
The product page on MF claims 28dB of isolation; I believe them. They're not only quiet, but comfortable -- big, deep, comfy cups that fit around your ears. They're tight, but I think they'd be OK for an hour or so. Comfortable even wearing glasses.
I'll be leaving this pair at work, because the office is pretty noisy. But I'll be getting another pair for home, for recording. A couple of times I noticed a little leakage from the headphones on overdubbed tracks. Not enough to be a problem, but I'd really like to be able to crank up the monitor volume without having to worry about it getting into the track.