It may be a small and silly thing, but I'm loving "Hello Cortana" on my 950. I found it annoying on the desktop (kept thinking I was calling to it, and suddenly browser windows would open to weird requests). But on the phone? Awesome.
For example... Heading to bed, pulling back the covers, settling in, etc. Phone is on the wireless charger on my night stand. "Hey Cortana! Wake me up at 6:00." Alarm set and ready to go. In the morning, when the alarm goes off, "Hey Cortana! Turn off alarm." Done. "Hey Cortana! What's on my schedule for today?" As she lists off my appointments, I'm getting up, turning on the shower, etc. A few minutes later, I'm at the sink finishing shaving and preparing to get dressed. "Hey Cortana! What's the weather like today?" Now I know what to pull from my closet. "Hey Cortana! Remind me to send an email to Bill when I get to the office." As I pull into the parking lot, the reminder pops up.
All that goodness without touching the phone. Love it. My daughter thought it was cool and tried it out herself. "Hey Cortana! Tell me a joke." Nothing. Silence. Cortana doesn't recognize my daughter's voice.
I know, I know... Other platforms do this as well. And I never thought I'd talk to my devices. But I'm actually kind of getting into the groove of it. (Now if only I could find out what Cortana is supposed to do on my Band 2. Why is it even there?)