The first generation Nests where pieces of junk. They couldn't do multi-stage heating and cooling systems, no humidity control. Not sure about the fan control. Really just a basic thermostat with wifi capabilities.
If I were to go with a wifi compatible thermostat it would be a Honeywell for sure.
A basic thermostat doesn't learn your heating and cooling habits and optimize itself to save money on your energy bill. That's the main selling point of the Nest. It's a bit harsh to call it a piece of junk just because it doesn't have the features you want.
For a "high end" price tag thermostat, the first gen couldn't even run a 2-stage air conditioner. The air conditioners that are highly efficient and will actually save you money on your energy bill. It didn't have the basic features of a $60 thermostat of that time. I would consider that junk. The "learning aspect of the nest" is much of a gimmick IMO and not needed. Constantly adjusting temperatures might not be a good thing (short cycling is bad), where its placed is crucial or it will give false adjustments (like a hallway). In Canada we are also on peak rate hours. It can't learn that.
The Gen 2 Nest is MUCH improved with features, but I would still be afraid of the compatibility issues with the more complicated ultra-high efficient HVAC systems. In this case I would go with the Honeywell Prestige IAQ.
