What is really so great about these?
Biggest complaints I have seen so far are:
If it knows you get up at 7am and like to have the temp set at 70 when you get up, it does not change the temp to 70 until exactly 7am. My current thermostat kicks in ahead of the set point to do its best to get the temp there BY the set point. The Nest is supposed to be so smart and 'knows' how long it should take to get to 70, have they fixed it to to be proactive? If I have to manually program it anyway to have it at the temp I want by the time I want, the auto programming isn't really helpful.
Lots of complaints about inaccurate temperature readings. Small package, big display, large battery = lots of internal heat to mess up the readings.
'Auto away' requires the thermostat to be able to 'see' you, and you must be moving enough for it to detect. Lots of complaints about it setting to 'away' while you are actually home. Working in your office, or watching a movie in the media room and temps start to climb because it thinks you are 'away'.
Seems you can get the same or better functionality (including smart phone control) from much cheaper devices, just don't get the love for these. Everything I 'assumed' the nest would do it turned out it either didn't do at all or had issues doing properly based in the real-life reviews I could find.
Though for me, until I reach baller status, I don't think I'll be investing in one of these.
The aesthetics are there, the ease of use is there, but it's still a first iteration product as well, so I know that within 2 years they will have a better one on the market. Thermostats last a long time. I've had mine for 2 years and plan on using it til I sell my place within the next 8 years. My place isn't that big, so that's prolly where most of the benefit is lost on me, besides the fact that I am going to move before 2020.
Overall, progress is good and having more connected devices is a plus. I do see this as a luxury right now and not helpful to a lot of people who think it has an appealing look.