I saw this actually on Best buy last weekend. I have a new laptop with Cortana. So I am just getting to know her. So far so good. I set it up so all I say is hey cortana (look ma, no hands) and she's ready for my command. Oh reminds me to connect it to echo via BT so Cortana's voice come out of my echo just for shits and giggles.
IMO, cortana powered windows is awesome. You can voice command everything. Open any app, settings, anything on menu. One thing I noticed. You can't use the word play to open youtube. It only works to the word watch.
I actually hate bing. So I just said hey cortana, open google. LOL. Surprised it opens it no problem coz when I type search google on Bing it's being shady.