I bought these for long haul flights. I've always had a problem sleeping on these journeys, and often cannot hear the sound from the entertainment system due to the high level of background noise.
And they work! On a couple of 12 hours flights from London to Hong Kong, I put on these headphones, switched them on, and sat there cocooned in my own small world of relative silence. The roar is stilll audible but only slightly. I could hear the entertainment systems sounds clearly, and when I wanted to sleep, I turned the volume down and slept well.
The noise cancelling was good enough so that when I removed the headphones, I felt deafened by the sudden roar that I hadn't been aware of. They were comfortable enough for me to sleep in (though not with my head on its side) which is remarkable for me, though after about 8 hours of continuous use, my ears felt a little uncomfortable. A quick trip to the toilet and a scratch of my ears made it all as good as new and there were no long term problems for me whatsoever which was good considering this was the first time I'd worn them. As a bonus, my ears didn't pop like they sometimes do.
For the negatives, I found them a little muffled but on an airplane, this was trivial. For the first time, I could watch movies without constantly adjusting the volume. For me, these headphones are great and I will not take long haul flights without them now.
EDIT: After a few more months using these headphones, I thought I would add a longer-term review.
In day-to-day use (ie, sitting in your living room listening to music), the quality isn't too good. Like I first thought, the sound is muffled.
But on transport like an aeroplane, they still are fantastic. There are three points to this: first, I can watch a movie on the in-flight entertainment system without blasting my eardums to pieces because the background noise is significantly reduced; and second, because of the lower volume of background noise, I can listen at a lower volume, hence less damage to my eardrums; finally, when changing altitudes, my ears do not 'pop' with these headphones on: they fit me well enough so maybe they form a nice pressure barrier around them.
I will not fly long haul without them and some spare batteries which last a very long time too.
The only problem I have is that the volume switch can be accidentally raised when resting your head back, but switch the headphones over, and all is well!
An excellent product that I do not regret buying.