I hate my thermostat. It either overcools or overheats my apartment by five degrees... most of the time. If it always did, then it would be predictable, and I could work around it. But sometimes it gets it right on the money. Then, if the temperature goes up a degree, the A/C comes on for two minutes and fixes it. Sometimes it will overcool or overheat by ten degrees. Ten degrees! That's ridiculous. That's the difference between uncomfortably warm and uncomfortably cool, except I had to pay to get that change.
I think I've figured it out: my thermostat must be provided free by Puget Sound Energy. They've deviously crafted a device that ensures that each electric bill is as expensive as possible thanks to wildly fluctuating temperatures.