Yes, it would be great if it would listen for "Computer" or "Siri" and then a command. Maybe it would have to be an option to turn on or off to save power, but for when I am driving, I don't want to have to push the button all the time. Maybe an option if it is moving or plugged in, then it will be on, but if it is sitting on a desk you would need to hit the button.
Oh, and it needs to have different accents. If Garmin can have lots of different accents, Apple can do it better. I also think they should have a Steve voice as a tribute.
So long as it understands the phrase "make it so" when asking for confirmation, I'll be happy