I was going to buy the 3rd Generation on Black Friday for 200 USD but I found refurbished units at my local Microcenter for 100 USD. The box are sealed from the manufacturer with a 1 year manufacturer warranty.
Main difference between the 2nd and 3rd generation are:
* A larger display (3.25 inch vs. 2.75 inch for 2nd Gen),
* A better resolution (229ppi vs. 183ppi for 2nd Gen),
* Slighly slimmer design (Smaller - 1.21" vs. 1.26" for 2nd Gen),
* All-new far-field sensor for viewing time and temperature information from a distance,
* Supports 5GHz wireless band (2.4 Ghz only for 2nd Gen),
* Furnace Heads-Up feature
Up to you to decide if those features are worth twice the price. For me, I was happy to save 100 USD.