I have a Nest gen 3. It's very nice and has many nice smart features. I have it wired up so that my OWB is H1, H2 is dummy wired to nothing (just a short bit of wire into the terminal, and H3 (* connection on the Nest) is my second/backup heat source, which is electric strips in the air handler). This allows me to set the eco/away mode down to 65 when the wife and I leave the house, and the thermostat will only kick on two levels of heat when we are sensed as home. The Nest has a 7* spread between H1 and H3. I also have the Nest tied into my IFTTT account so I get a text message if the house gets to 64 degrees for a low warning and 74 degrees for a high warning. I also use Nest manager from gethub to tie it into my Samsung Smatthings home automation. This allows routines to be run, turn on/off lights with house temperature reaches certain point, ect.