I can't help with the wiring but I have a first generation nest thermostat and it has been great. You can get pretty detailed in how you want it set up, you can set up a geo fence so that when your household phones are out of the area it will shut down to your "not at home" settings, and then resume when you return. I don't use much of those features though, I just like the scheduling aspect of it because it is easy to setup and works well. I also like being able to adjust it from my phone.

This model didn't need any extra wires. I pulled down a 30 year old thermostat and mounted this one right up no problem.