While driving with Bluetooth headset, having texts read and responding verbally. Or just dictating texts.
I use reminders are a lot. They will be even better when the snooze option is added to location based reminders with 8.1 update 1.
The news function works well.
I can't use quiet hours, since I need to be able to take emergency calls from unknown phone numbers at night, and during meetings where I don't want interruptions, quiet hours isn't restrictive enough. If I didn't need to be available for emergency calls at night, quiet hours would be awesome.