I've only been using them for a hour or so but so far they are almost equal to my old Sony MDR-100ABN headphones and less than half the price!
I brought the JVC noise cancelling headphones a few weeks ago and had to return them as there was a buzzing sound in the background and those were £90! No buzzing with these.
About to use them on a flight which for me is the real test for noise cancelling headphones. If they aren't any good for flying, I'll update this review. No update = good for flights