I have owned a set of these for close on to a year now and let me just say that they are the most comfortable things I have ever worn. Seriously, I can wear them 12 hours at a stretch, no problem. Music reproduction for me is fine. However, when I crank them up to full volume, people in a room across the hall can hear them... Noise cancellation (both ways) is non existent. Not a problem for me when blasting my poor ear drums though haha.
I bought these because I have a decent on board soundcard and I recommend them to people in my store looking for a nice mid range headset that doesn't break the R1000 mark. And this is coming from a guy who doesn't like Razer products in general. Unfortunately, Logitechs offerings in headsets leave a lot to be desired.