Sorry for the fake Echo effect:) Got one of these for the kitchen and so far am impressed. As usual with Amazon stuff it came pre-setup with our account details, so plugged it in and connected it to the Wifi and it just worked.
Voice recognition is good. We have a large kitchen and the Dot is positioned on a shelf near one corner. There is no problem getting it to recognise voice commands from 15 or 20ft away. I mainly use it to listen to various radio channels (using TuneIn radio) and Amazon Music. Being able to operate it purely with voice commands is great in a kitchen, where your hands are either wet, or covered in food.
I haven't bothered to connect it to a bluetooth speaker yet, as the built in one is adequate for kitchen use. I may end up transferring our Google Play music subscription to a Spotify Family one, since the Dot can connect to Spotify, but not Google (no surprises there:) However, I find Amazon Music had improved recently and most stuff I want to listen to is available from there.
Don't have any smart lights, so can't comment on how it works with SmartHome stuff. Having three children who think that light switches are don't have any off function, what I would like is an app that monitors the lights in each room they go into and then if they go out of the room without switching the light off, calculates the amount of electric used until someone comes along and turns the light off. The cost of the electricity should then be transferred directly out of their bank account into mine!
Edit: Just found out that if you buy the Audible narration for a Kindle book, you can listen to it on the Echo. I haven't subscribed to Audible in the past because I didn't want to be tied into a subscription model. However, if you go to the Audible login page and log in with your Amazon account details, you can see and play any Audible books that you have bought together with a Kindle book, no subscription required. In fact it looks as though it's often cheaper to buy the Audible book together with the Kindle book, rather than buy the Audible book on its own.