I have a set. They sound amazing and since I travel alot they are perfect for movies and music without getting hotel neighbors mad. I would have paid 300 for them and found them to be worth it but they seem to be all over craigslist and got mine for 160$.
Noise cancellation is amazing. Can't hear anything outside of them. To the guy who made the powered headphone comment. One, the powered portion is what powers the noise cancellation feature. Two, I have never owned a pair of headphones with good bass that weren't powered. Those drivers need the boost.
As for the leaking. Yes if you crank them and sit next to someone they can be heard. Its not obnxious and is barely audible if listened to at a reasonable volume.
