Being able to say "Xbox On" and the console/tv/cable box all turning on at once in response is reason enough to keep it plugged in.
Or, you know, you could just press the Xbox guide button? Same level of effort with less frustration.
Does that work as well? Neat. I haven't been frustrated with the voice stuff when it comes to turning it on and off. I walk in the room, say "Xbox On" and by the time I sit at my desk where my controller usually is everything is turned on and waiting.
If it worked on the 360, I see no reason why using the guide button wouldn't power on the Xbox One. Microsoft has to know at this point that not everyone is willing or able to use voice commands.
Oh I meant turning on everything. I know it certainly turns the console on.