Isolation is average - sitting 20 feet from the dishwasher, the highs disappear and the other most irritating parts of the sound are definitely suppressed, but the biggest overall part of the noise remains. If I had to rate it compared to around-the-ear closed headphones like the Philips L1 and the ATH M50, I'd say it's not as good but not a lot worse. Does a good job for on-ear I think.
Leakage is pretty low - I put some rock music tracks playing that had a constant sound level, fairly loud, then I pressed the earcups against my leg so they would be sealed about the same as on my ears, and I could hear the sound faintly by getting my ear within an inch of the earcups. The best test is in bed - I didn't go loud there, but at moderate volume the person next to me could not hear anything. You could use these in any office cube and play at a good volume, no problem.