The T9 is a very nice, feature-rich smart thermostat. The feature that won me over from the Sensi stats, which I had been using happily, is the T9's ability to use remote room sensors. These really add to the usefulness of the thermostat. There are numerous other nice features, such as an ability to program a minimum cool or maximum heat setpoint, which prevents the kids (and elderly) from setting an extreme temperature in the mistaken belief that doing so makes the system cool or heat faster. The biggest downside to the unit is its reliance on a 'C' or Common wire for power, which is frequently not present or not hooked up at the equipment side. Honeywell/Resideo as addressed this by kindly including a special wire-in module that can deliver the necessary power, but this is in my view unnecessarily complex. Most other smart thermostats eschew this in favor of simply powering the thermostat with a couple of batteries. All in all, a very competent and useful thermostat.
I am enjoying the ease of using this thermostat, from phone or on the wall. It not only allows me to set up parameters for heat and cold, but a second sensor allows creating a range for two areas at once.
Extremely easy to install. The room sensor takes multiple temps and creates and average temp so everyone is comfortable. Easily connects to Alexa. Sleek design