Have:
Adding things to my shopping list (via Alexa - currently in the kitchen and bathroom - two most frequent rooms where I'm like "hey I need more XXXX")
Changing the temperature (Nest via phone app and command line tool I wrote, and now Alexa just did a native integration)
Finding out my schedule for the day.
Finding out the weather forecast for the day.
Playing music (via Sonos or Alexa)
Locking front door when I'm going to bed.
Getting notified of movement or sound in the house while I away (Nest Cam and Smart Things)
......
Like the OP I'd love to have the voice control available in any room of the house. I'd love to have better security features (i.e. if I drive up my driveway at 3 AM turn on the outside lights, if a stranger drives up my driveway at 3 AM WAKE ME UP WITH AN ALARM). I'd love better voice controlled Sonos music selection. Composing emails, having handsfree phone or video calls, warming up the oven at a certain time, etc...