I don't own one but like with the LUX X9000TS model I've saved a lot of money from this $43 thermostat with Touch Screen Programmable Thermostat Touchscreen Interface
Features
7 Day Programming - 4 Periods Per Day
Vacation Hold
Smart Recovery
Lighted Display
Touch Screen Lockout Code
2 or 5 Minute Delay
Temporary Temperature Override
Fahrenheit or Celsius Temperature Display
12/24 Hour Clock
Filter Monitor
Energy Usage Monitor
I had new Carrier Central AC unit installed in end of the summer of 2011. That already is Energy Star. Save a lot with it. But the thermostat I got wasn't fancy it had LCD but that was it for Honeywell.
Buying the LUX TX9000TS model saving much more. But the only feature this doesn't have is WiFi to pull in off the internet the current temp outside. So you would save more with a thermostat like that, than one without it. Since the one without has to go by what the current temp is in the house.
Could be like 80 F indoors where outside them was 75 F. The LUX would run the AC to bring it down to say 77 F is what I've set mine to be. I find if I set the it 76 F I have to pay extra $30 a month. Just to reduce too 77 F and save $30 a month.
Nest and LUX would work about the same both would give me more information about system and how and when to change the AC indoor handler air filter. This is very important as a clogged filter would use more energy.
Nest would win with its fancy high tech looks and WiFi internet current outdoor temp features as the LUX Smart Thermostat doesn't offer such features.
Nest extra $207 cost just to have WiFi Internet and high tech looks, still pricey to me. Even the top-of-the-line LUX with Wireless Remote still doesn't have all the features. I need a large display Amber Blue LCD, Nest has Multi-Color LED display uses less wall space. LUX 9600TS has much larger display than my LUX 9000TS but mine is large as well easy to see the feature controls.
When the LUX is running it greets you with a message MORNING as some extra graphics in LCD dark contrast fashion To let you know AC Cool is running. SYSTEM ON or SYSTEM OFF. Shows the day of the week, time and large temp readings for the current ROOM. Can be set to a calibration to zero. My old Honeywell didn't have that feature.
To me right now LUX will be the only thermostat I'll be using for now. NEST needs to drop their price down to $100 or $150 bucks. $250 is a lot for a thermostat. How much would it save me about the same $30 or maybe $40 with outside temp readings. Right now most non-WiFi units would use a wire that would be attached to the AC unit fan compressor outside at additional cost.
Review here on Techspot well done for the NEST, the prices of the NEST is the only reason why I wouldn't jump into it as the LUX does the same for $207 less except without multi-color display and WiFi internet temp.