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.
The simplified experience is nice. While installing, it showed me which wires were misaligned. Simple to use, really like the multiple room sensors. Miss the customizable colors of the previous Honeywell touch thermostat. Overall, great thermostat.