One thing the videos should have done is show Cortana for Hololens. I think Hololens should have a 3D Cortana like in Halo that interacts with you like it does on windows 10. She could remind you things, you can tell her to send an email or look up something. It would totally be a Siri killer if they develop this. I imagine it would be possible to develop a 3D GUI for Cortana and have it run the same back end as the desktop. This would be an awesome way to advertise for the hololens and MS in general.