I bought the Echo and a WeMo controller at Staples this week. My biggest problem so far? Keeping my wallet in my pocket. There's just something about being able to say, "Alexa, nightstand light on." and having it JUST HAPPEN that makes me want to do it for every light in the house. I've had a lot of fun telling it to set timers and alarms and asking it stupid questions too. It plays music better than most bedroom audio, but of course can't replace a high end stereo. I am surprised to not find any way to add cellphone service to it. "Alexa, call 911" seems like a no brainer to me.
Complexity is similar to setting up WiFi for individually controlled outlets. Bump it up to assembling Ikea furniture if you venture into controlling groups of outlets at a time. So, not so simple that a toddler can build it, but once set up, pretty easy for a toddler to control it.
At $180 per Echo (one per room), $50 per AC switch, more for other types of controllers and sensors, it's not cheap for a whole home. Particularly given the likely limited useful lifespan. That said, it's still a middle class purchase. Comparable to a couple of flat screen TVs, except that you can buy it in pieces and spread out the "payments" over as much time as you like.
Now, how do I get it to CONTROL my big screen TV...Hmmmm :)