I really like them. I've only owned some JVC noise cancelling headphones, some Phillips and listened to the Bose QC15's. And the PSB's sound is in another league compared to the others.
I like that they have 3 modes, passive, amped or amped with ANC. They sound great passive, and even better from an iPhone with the inbuilt amp switched on. I do alot of flying and the ANC works really well. I don't use it any other time though.
I've had an issue with the headband cracking and apparently it's happened to a few others. Mine are being replaced. I've heard that its being looked into and maybe a new headband is on its way. Other than that they are great.