I think they sound great, but I'm not really qualified to speak as an audiophile. They are very clear for the stuff I listen to, and the headphones definitely block out surrounding noise.
Unfortunately, I don't wear headphones very often though... as an IT guy I have to keep my ears open for the phone and walk-in requests for support, but I LOVE the Play360! I have it hooked up to my laptop while I wait on the Lumia, and it has really nice sound. I had it going for 6 straight hours on Sunday while I was reading the forums and cleaning up around my apartment. I've used it throughout the week for some music in my office.