I have been using CEP's with my David Clark ANR headset now since 2007. Flying between 60-120 hrs a month. I had an issue for a while with them applying too much pressure on my ear cannel (DC headset applying pressure), but I bought Oregon Aero ear muffs and have not had an issue since. My CEP lasted me until last week when one of the transducers pulled out of the housing. I got in touch with CEP-USA and they very happily sent me a replacement.
I can tell you that for me they are superb, great audio clarity and noise protection.