I love many things about my Surface headphones. They sound great, the noise cancelling is wonderful, I can wear them all day long, and they even look pretty cool.
I work remotely and am on calls very, very frequently. I never say "okay Cortana" during my day. In have Cortana disabled on my computer.
However, my headphones pick up other things that I say and things that other people around me say as the queue phrase. This, in turn, interrupts my calls with the people who I am speaking with.
A huge part of my job is instilling confidence in the people with whom I am speaking. Having calls interrupted by what is easily perceived to be my technical incompetence does not instill confidence.
I really need a way to disable Cortana on my Surface headphones or I will seek to return them.
I feel very strongly that if the Cortana feature does not work flawlessly that it should not be something that cannot be turned off.