I've got two as well, in separate houses. 1 house is used an office, and its nice to turn the heat off if nobody is there for an extended period of time without having to go the the house.
We didnt want to buy a second one, as at the time we were ordering them from the US- before it was available here in Canada) so we tried the honeywell one from HD which is wifi compatible. I was a pain in the *** to install, and after 2 hours I gave up. It required me to re-wire something in my furnace. I ordered a nest, and installed it in 2 minutes, and its flawless.
Both mine are 1st generation. My new house is going to get one too! After using it, you cant go back.