The NEST is great.
Here is my review - $240 in the summer is my highest electric bill and I live in AZ with two A/C units and my home is 3,200 sf. Set up the Nest correctly and it works. The app is fantastic and I like how it integrates with the Nest Protects Smoke Alarms that I have replaced in my home as well. It also fun to play with my wife when I am out traveling for work in another state and I can turn the temp up/down when she is not home.
Dessert Appllo about
Nest, v5.9.2