The Ecobee3 appears to be a very highly rated thermostat and I must admit it does have a lot of good features and user controlled parameters. My reason for purchasing one was my geothermal vendor recommended it. The standard ClimateMaster thermostat, and many others, operate on a 1 degree Celsius differential. As a result our system was taking an extremely long time to recover that one degree and get back to set point. During that time we sometimes sensed some discomfort. The Ecobee can be set to as little as .3C differential and this resulted in a more even temperature at the beginning. Something has changed and we began to notice that the house would get a degree or so warmer than desired. Using the thermostat, 3 remote sensors and two weather monitors, all in the same area, we noticed that the thermostat was reading lower than all the other monitors and by the time the tStat reached set point the house was a bit too warm. Using the Temperature Correction parameter I adjusted the thermostat to +1.1C. This resulted in set point being more accurate but now we noticed that while all the other sensors in the room had reached 21.7, the point for a call for heat, the thermostat itself read higher and did not call for heat. As a result the house would get a degree or so cooler than desired before the heat kicked in. Ecobee insists that the thermostat is working correctly and is designed with a margin of error of +/- 1C. Does this seem reasonable? How can you get an instrument that is sensitive to a tenth of a degree but has a margin of error of 1 degree. I have a ton of data that shows my three remote sensors all within .3 degrees of each other while the main thermostat is as much as 1.3 degrees different than the sensors. I find it even more interesting that the two weather stations within the room are more in line with the remote sensors suggesting they are the more accurate. The question has been raised about my expectations before. Are they too high and should I be content that my system runs for a significant extra amount of time and over heats the house or that I shiver (exageration) through an hour or so before my system kicks in? I look forward to any comments, especially from other Ecobee users. By the way, for the purpose of monitoring the room temperature, all three remotes were disabled, so as not to introduce any averaging effect, and brought into the same location as the tStat.