I originally bought these headphones for airplane rides about 6 months ago. However, I found it didn't cancel out all the airplane noise as well as my JBuds J2 did. I noticed I had to turn my ipod volume up higher with the Sennheiser than with the JBuds. However, I still really like these headphones. While they may not be the best noise cancelling for airplanes they are awesome at cancelling out background noise such as tv or people talking. I listened to them at my boyfriend's parents house when his parents (who listen to the tv louder than my grandparents do) watched tv. I was amazed at how much of the noise it cancelled out!
My favorite thing about the earphones is how you can use them without the noise cancelling feature. Sometimes I want to be able to tell when other people are trying to talk to me. That was one of the main selling points in buying these Sennheiser headphones compared with other noise cancelling headphones .
As for the sound, I am very happy with it. I am not an audiophile by any means but I absolutely love listening to music and these Sennheiser headphones sound amazing to me.
My only complaint about the headphones is that they tend to make my ears hot. I guess that's how it is with a lot of noise cancelling headphones though since they have to completely surround the ear. When I was living in Hawaii it was more of a bother, but now that I'm back in Washington where it's not so hot I don't find it as annoying.
Overall, I highly recommend these sennheiser earphones. I did a lot of research on noise cancelling headphones before I decided to buy these and I am still happy with my purchase. While they are expensive, but I think they are made well and if you take care of them they should last a while.