Excellent sound quality & good noise cancelling capabilities.

I bought these headphones about a year ago and absolutely love them. I needed a pair of headphones to use with my work computer and MP3 player.

Comfort:
They are comfortable to wear in a setting where you won't be moving around too much (I use them mainly at work). They would not be appropriate for use while running or working out.

Sound:
They sound spectacular with and without the noise cancelling turned on, although quality does get a boost with it on. All frequencies sound crisp to my liking, but I am not a avid listener of fine classical music so I don't have an impeccable ear for the slight imperfections in sound quality that others may pick up.

Noise Cancelling:
Through a little bit of research I have determines that most noise cancelling headphones reduce external noise by -12dB. These headphones appear to accomplish this using microphones on the outside of each headphone and padding on the parts that sit on your ears. Most products (including this one) reduce certain noises (such as airplane noise) almost completely, while few if any are very successful at cancelling out all noise (such as the human voice).

Battery Life:
The noise cancelling feature required a single AAA battery that lasts about 12 to 15 hours on my NiMH rechargeable batteries. I find this to be acceptable and often use them without the batteries when they die.