I have had the 3M-50 for almost 4 years, which is pretty rudimentary in terms of features. It does, however, have a plugin for my vera lite, so I do like that. It uses the Radio Thermostat servers while you are not on your WiFi/network and there is a polling interval of 5 minutes, so there is a delay of up to 5 minutes in terms of interaction with it. They have a nice android app interface and widgets to add to your home screen. I would say my only real problem with it is that it is a little temperamental when detecting if you are on your WiFi network. Sometimes it takes several refreshes on the app to get it to detect. Sometimes, I have to close the app and reload.
That being said, I am looking at the Ecobee 3 with a couple of sensors. I did read about some issues with the thermostat generating too much heat and causing the thermostat's reported temp to be much higher than the ambient temp actually was. I don't know if that was resolved or limited to a specific batch.
I looked at the Nest and decided it wasn't for me. The adaptive schedule thing isn't that big of a deal for me. Also, at that time, the swing temp was either not adjustable or was not adjustable below ~2 degrees F. I like to roll with a .5 degree F swing temp so the thing turns on and off when it hits the temp I set.
A coworker just got the Sensi from Emerson and he likes it. It seems cool from what I can tell. It also has dual schedules, which is nice if you are like me and have a need for 2 schedules. Other than that, I don't know much else about it.
