I have the Nest thermostat. It was very easy to install. It also works pretty seamlessly with the Echo, so I can raise and lower the thermostat or set the thermostat to a specific temperature. However, I cannot ask, "Alexa, what is the thermostat's temperature?" Does anyone have a different thermostat that allows you to ask what the device's temperature is currently set at? Does the ecobee3 support this?
Oh, one other issue I sometimes have with the Nest is that if I don't walk in front of it for a period of time it goes into "away mode" (i.e. it thinks I've left the house), and goes into an energy saving cooling/heating cycle, and when it is in away mode you can't change the temperature with the Echo. This is pretty annoying. I notice it is in this mode when it starts getting hot, but I can't have the Echo set the temp --- I need to get off my butt and walk in front of the Nest.