Hi @kenny_Powerrs,
Here is my take on your question about WiFi thermostats such as ecobee3.
On my side, I have a z-wave thermostat (CT30) for a gaz fireplace and an ecobee Smart for my HVAC.
My z-wave thermostat is totally controlled by ST, I only use it to start my fireplace in the evenings when the outdoor temperature is quite cold.
Otherwise, my experience with a z-wave thermostat is the following: very slow UI response and very often no response at all. Why z-wave thermostats are not responsive? It could be an ST issue or simply a z-wave thermostat issue. The fact of the matter is that z-wave thermostats are just plain dumb and they only work for specific use cases. As soon as they are connected to a home automation like ST, you cannot program them.
On the other end, smart WiFi thermostats are more versatile and responsive. You can use them on a day to day basis by changing their setpoints via the UI w/o problems. You can also use their own scheduling capabilities to set your home/away/sleep schedule in general and then use ST to change their program on the fly when your schedule changes (ex. you’re away at a given time when you’re normally home according to the ecobee schedule)…
On more thing about the ecobee3, soon you’ll be able to integrate its remote sensors to ST as motion/temperature sensors thru the custom ecobee device that I created. This way you don’t need to buy additional sensors for your bedrooms for example.
For more details, please refer to the following thread. There are many smartapps that I have developed for the ecobee thermostats.
To conclude, there should not be any conflicts between ecobee and ST if you let each platform do what it does the best: ecobee owns the general thermostat schedule and ST manages the exceptions when you’re away or home (according to its hello home modes) and ecobee does not expect it
In brief, if your main factors are reliability and efficiency, then don’t hesitate to choose an ecobee thermostat over a z-wave thermostat. Most WiFi networks are very reliable now, and this issue should not be part of your decision making process.
If you have any other questions, let me know.
P. S. I created the custom ecobee device so that it works flawlessly with ST for my own home, and exploits all the richness of the Ecobee APIs.