I have a Honeywell programmable thermostat attached to my gas furnace and central air. It was less than $100, has a touchscreen and can be programmed for 4 different time ranges, 7 days per week. It does not have WiFi or a high-res color display on it - but it does the job. It's supposed to have "smart response" technology, where it learns how long it takes to recover a temp - but I find that to be less than effective and often find it "in recovery" after a programmed temp change.
In the winter time, it definitely helps reduce my gas bill as the gas heat can warm the house several degrees in less than a half hour. In the summertime, it's not worth it - it takes way too long for the AC to cool down the house on a really hot day and I'm not convinced that allowing the temp to vary so widely really saves energy. I used to let it warm up to 80ºF and during the times I did, it wouldn't get back down to 73 or so until the sun went down and the outside temps dropped - usually hours later. And during that time, the A/C was running constantly. I just leave it 'on hold' at 73ºF and honestly, have not seen much variation on my electric bill.
I looked at the Nest at one point and it really seems like overkill for a thermostat - and of course, it isn't cheap. At less than $100, a Honeywell thermostat offers ¾ of the functionality for ¼ the price. And now you needn't worry about Google glass spying on you