Our home has four furnaces and three air conditioners configured into five zones (1st floor, 2nd floor, master bedroom, basement, and shop).  Two of these are now controlled by Nest thermostats replacing the programmable Honeywell controllers I installed when we first moved in.  Our local natural gas provider was offering a $150 rebate on each device which motivated the purchase. The new thermostats are much more elegant in appearance and far easier to program and operate. It took me about 20 minutes to install each and I will add additional units when rebates are offered again.