Nobody talks to Cortana
I use Cortana a lot on my phone but I only talk to Cortana in the car. The rest of the time, I type my questions/instructions. Obviously, I don't want to do that while driving but I find it's by far the best option.
Cortana's added-value searches are pretty good and I get to control them precisely with my text rather than have a back-end on Azure try to guess what I wanted or get it wrong if I happen to sneeze or be eating a mint or whatever.
I can see typing to Cortana becoming useful on the desktop, especially given the extra bells and whistles they're giving it. That thing about searching for a restaurant on Maps and getting not only the location but also (optionally) opening times, contact details, reviews and menus? Handy.