I purchased the T9 thermostat with one remote sensor, then added 2 more. I think the use of more remote sensors has added to the efficiency of the unit. I've noticed the temp is more steady through the house throughout the day, and I like the auto sensing, so it will switch to heat without me having to remember to do so.
I've got a remote sensor in my living room, my main bedroom, and my home office. Through the day, the temperature in the house is averaged based on the "active rooms" (those with motion detected) only. For instance, it is Sunday as I type this, and no one has been in the home office, so that sensor is excluded from the temperature average. The T9 is basing the house temperature only from the main bedroom and the living room sensors.
All in all, this should help keep my home more comfortable, and even better, help to reduce my energy costs.
At night, I've programmed the T9 to use only the "specified rooms," not the "active rooms," and have specified only the main bedroom remote sensor until 6:00 AM. At 6:00 AM, the system returns to "active rooms" and uses the rooms that have motion.
So far we like this thermostat. The remote sensor allows us to help manage the temperature in a guest room when it is occupied. When no one is staying with us, the thermostat ignores the temperature!
The screen and phone interface are pretty straight forward. We have a Honeywell Lyric in the other level of the house and while not as stylish, we like this model better. We manage both thermostats remotely with our phone from a single Honeywell app.
It's a very sophisticated thermostat. I would have given it 5 stars except that the instructions on how to install it in an older home are useless. Resideo does have a help line, but getting through requires a wait time only a person of total leisure might have, certainly not one who has a job. Besides, if you have that much time on your hands, you probably can afford an electrician to figure out the installation. It was a bear requiring a great deal of self-education and an external 24 volt power supply. However, once installed it was recognized by my WiFi and has worked flawlessly.