Yeah same here. I have an 8000 sq ft home with 2 Ferraris. Plus I have a 1000 sq ft gazebo next to my 2 hole golf course. Gonna have to pass.
If that is true, then you aren't hurting for money. And though I'm not suggesting you shouldn't be frugal, my guess is you could upgrade at some point without issue.
I have 2 of the Nest thermostats and they are pretty good. I do get a little annoyed that they are not as smart as I would like them to be. When I turn the temp up or down and five minutes later it hits one of its "learned scheduled events, based on my past habits" it will adjust the stat, and it shouldn't. It should realize I just overrode the schedule and to go with that. Likewise, I know that the stat has access to the outside temp, but it doesn't seem to adjust the temp based on that information, more on learned scheduling.
I currently have 2 in my house. But I have 5 thermostats as I have a radiant system with a stat for each zone. And so these only control my heat in the winter. I put them in the two upstairs zones, and haven't decided if I plan to update the other 3 stats. I would like to for a homogenous system and look, but don't see the point in outlaying $750. They really haven't come down in price.
Likewise with this, $129 is steep. I have 7 or 8 smoke detectors in my house. At $59 to $79 each, I could see doing it. I hate the chirping. But not at $129 a pop.