It's funny - we've been remodeling our house, and as part of it, added a bunch of z-wave compatible switches. I was moving some stuff back in (we've been out of it), walked into the house at night, and after living with an Echo and a Google Home for the last year and a half, had a very strong urge to say "Hey, Google, turn on all the lights." -- unfortunately, I hadn't moved the Home in yet! :) I was carrying a large box and it would have been fantastic.

My experience with both devices is that there's no one Big Thing, except maybe music. There's a lot of stuff that just works surprisingly well by voice. Quoting my daughter: "Hey, Google, play Puff the Magic Dragon" - "What's the weather today?" - "Turn on/off the lights" - "Set a timer for 5 minutes" - "What's 17 tablespoons in cups?" - "How long does it take light to get to Mars?"

It's probably not smartphone big. But I think that in the long term, we're going to find that some kind of voice-based interactive device like this will become very common.