I really like the Honeywell system. The only problem that i see is that it goes offline at times. Everything else i have on wifi stays on. Other than that, great system.
I've only had the product for less than a week so I can't give it 5 stars yet. It is working well. One draw back is that for the best performance it has to be connected, in my case, to the Wifi router, something that I wasn't told and not used to.
Your purchasing options are not fleshed out enough. I bought my Honeywell thermostat from the Heating company I work with - they'd just installed a new furnace and my main request of the thermostat was that I be able to access it via wifi.