The Nest thermostat is a cool idea. From the outside, it looks beautiful, has a nice screen and is cleverly done. It is an improvement to the old Honeywell thermostat torture pads. Those Honeywell devices ran the dungeon in computer-overlord land. Humans were placed there to program them to change the temperature.
The problem with the Nest is it's overly complex with its twisting turning mechanism and selection of options on the screen. It's very coarse and difficult to control with your hand, and it's complicated trying to find options. I recognize based on the input mechanism that was what they could do. However, the entire device can be replaced with a sensor, a microphone, a speaker, and an optional small display.
The Nest thermostat companion app is a crutch that shouldn't exist really except for those cases you're using it remotely. It should be completely voice-enabled. If I want to say I'm away, then I say “I’m away”, if I want the temperature to be 72, I say “72”. It should repeat back to me confirming what will happen.
From a cost point of view a sensor, microphone, speaker, and Wi-Fi module is all that is needed (and maybe a small display). That’s low cost. The existing nest is way too expensive. Dump the interface way to interact.
Nest you're under arrest.