Haven't done the thermostat but we do use Alexa to operate lights in the home. It's actually quite convenient... particularly when you get old and fat and don't feel like stretching over the sofa and end table to reach a lamp. Much easier to tell Alexa "Living room On/Off".
Wife uses her iPhone app when returning home at night to turn on the lights before she enters the house. We also use Alexa for background music in the house.
Alexa operates our Sony TV on/off and volume but it's actually easier to use the TV remote than voice commands. We also have an Amazon FireTV 4K with voice remote. Now that voice remote is awesome for finding programing within the different apps like YouTube, Amazon video and Amazon Music that we subscribe to. Any album, any song... anything. Just say what you want and it's starts playing. Where was this when I was spending a fortune on records, 8-tracks, cassettes and CDs?
Use Alexa timers and reminders every day... for all sorts of things. The other day when it was smoking hot outside the dog wanted out. I told Alexa, "Remind me to let the dog in 15 minutes"
15 minutes later... ding ding... Alexa says: Reminding you let the dog in.
Amazon Echo is great. We have them throughout the house, garage and shop. I have an air compressor in the shop with an airline that runs under the house to the garage. The compressor is connected to an Alexa wi-fi switch. When I want air in the garage I just tell Alexa "Compressor on
". Beats the heck out of having to walk down to the shop to turn it on, then again to turn it off.
Amazon Echo is one heck of a convenient and useful device for us.