Pros: If you need cancelling, they kind of work
Cons: Passive cancelling beats these
These were actually supplied with a Sony X-Series Walkman, which has built in cancelling. The headphones themselves have little mics on the back, and this is fed to the Walkman using an ordinary headset plug like you'd expect a handsfree kit to have. To be honest I've never found the noise cancelling feature to be useful, and even if I did, any headset with a mic in it would be a better choice, such as one by Etymotic.
The sound itself is far too lacking in bass, although the highs are brilliant without being sibilant. You can fix this to some degree with Sony's excellent DSP and equaliser options, but the best fix is to just put these in a drawer and pull something else out. Perhaps ironically, Sony's cheaper players come with muddier but far more enjoyable earphones.