After researching all the HomeKit compatible options over several weeks, we settled on two of these units and am extremely pleased. We didn't want a hi-design "look-at-me" wall fixture; we wanted a functional and subtly attractive thermostat that was easy to install and HomeKit compatible.

The accompanying bonus we received from ecobee is the surprisingly in depth metrics via their HomeIQ section (via the web site or the ecobee iPhone app). Great stuff...we've already gone through three revisions on the schedule cooling sections -- ideally, all leading to greater utility bill savings.

HEAT-PUMP warning: The only gotcha we ran across in the installation is our units are heat-pumps (we live in the Southeast where these are common...across the rest of the nation...not so much). Long story short, make sure you:
a) DO NOT set up your ecobee as anything other than a heat-pump (no boiler, no furnace...these are somewhat defaults for ecobees when they install)
b) When you examine your prior thermostat's wiring guidelines (prob on the inside cover)...our thermostat "assumed" we did NOT have a heat-pump and had a default wiring guide (W,R,C, etc...) for either a furnace or boiler. ONLY when I looked waaay down on the cover and in tiny, lightly shaded font, did I find the wiring-conversion for if you have a heat-pump.

I bought this to add to my home automation. Unfortunately I have to agree with others that have observed inconsistent temperature results. I have a weather station display that sits next to my chair in the family room. I have verified the accuracy of the indoor temperature reading of this display. I have set the Ecobee 3 to 72 degrees and on most days it will keep the house comfortable. But on some days it will only get the house up to 71 degrees and some times, like today, only 70 degrees. Which I find slightly uncomfortable. You never know when the thermostat is going to deviate from the set temperature. I think for a thermostat in this price range this is inexcusable.

Another problem with this thermostat is if you bump up the temperature it stays at that temperature forever until you tell it to go back to its programing. This is a pain because it no longer will provide the cycling that saves energy. My previous programmable thermostat would go back to its programming on the next cycle and was half the cost of this one.

This was easy to install. I say this because my AC system had a common wire already so I didnt need to mess with that Power Extender Kit. Also, I have a Red wire but I dont know if its Rc or Rh, but read that you hook it up to the Rc anyway as its internally jumpered as needed. It comes with a nice face plate that covers up the previous holes which was necessary for me since im on the 4th thermostat of the house. Unfortunately, my house has a standard electrical box for this thermostat location and the face plate's mounting holes isnt spaced for that. I had to use the top hole of the face plate and place a strip of wood or plastic behind the project box bezel, then anchor a screw into this using the bottom face plate hole. It was awkward getting this done but it was secure afterwards. I love the features of this unit. I can set 3 different standard temperatures (home, away, and sleep) and set these levels at multiple times throughout the day. I can also program vacation times to override this. It can also be set up to sent you a notification if the thermostat goes above/below a threshold to warn you if the system isnt working. This can all be done from your smartphone.

The only downside I have with it is that the screen isnt nearly as high resolution as it should be. First world problems.

I was very enthused after installing this and, in practice, seeing that it was going to work well for what I wanted. I was going to be able to monitor my south Florida home for the 6 months that I wouldn't be there and easily switch schedules at will. It worked, mostly okay, for three days. Then it seemed quite a bit warmer in the house than the display was showing and, when I tried to access it, it was not connected to my wifi. There wasn't much that I could make it do from the interface. Pulled it off the wall, waited a while and reconnected (reboot). After even letting it try overnight, it never would fully reboot ... just kept stretching its wings. It was borked. Returned it to Amazon. No time to try another unit right now. I will probably try it again at some future date if quality control/reliability shows improvement.

I've only had it for two weeks but I really like it so far. The installation was quick and easy. I had a proper wire running to my old thermostat but they didn't utilize the C wire so I had to hook one of the extra wires up to the C wire on the furnace panel and the rest was simple. Took maybe 2 minutes to link it to my wifi and setup the my account then another couple minutes to play around with it on my phone to figure out how to set the schedule. Overall the installation and programming took about 30 minutes so not too bad. I haven't seen an energy bill yet to see any savings but I personally bought it for the programming and being able to control the temperature from my phone since I live in a three story townhouse. It's annoying to realize when we are in bed that my girlfriend left the heat on high so I like just rolling over and resetting it to the schedule without getting out of bed and walking down a flight of stairs.