We had four thermostats installed and one wouldn't connect. It was replaced and the new thermostat worked. The T6 was easier to set up then the previous Honeywell Wifi thermostat, but I did like the old app better than the new one.
My A/C guy recommended this thermostat. Easy to install (my A/C guy walked me through it). I love all the features. Very easy to use. Great thermostat for the money!