Noise cancelling technology are isolation on headphones as to what ankle warmers were to practical fashion sense in the 1980's - both are fads and don't really make any sense.
If I ever needed isolation, a good sealing headphone or canalphones have always done the trick for me. It seems companies these days love to throw it into anything because people will just buy it just for the sake of it (Beats Studios anybody?).
Actually Bose QC15s cancel an amazing amount of noise. This is pretty irrelevant on head-fi since most people here are 100% focused on sound quality. That is how it should be, but unfortunately I am in school right now and without the Bose I would not have a place to study, but with them I can study anywhere. The noise canceling is that good. I haven't heard anything that compares, including the beats, and I agree that people are buying into it just because its the thing to do these days, but believe me the Bose actually work and I did not get them because its a fad. I got them because I was fed up at the loud ass people that go to my favorite cafe and ruin my focus.