Recently got the Ecobee 3 lite, and so far have been very happy.
Picked that over the Nest as it seems that it gives a little more control over various thresholds etc. My system is a little more complicated than the OP's as I have a heat pump with a gas furnace as auxiliary heat and the Ecobee lets me set how long the heat pump will run for before calling for the furnace as well as a load of other settings.
For a single heat source a standard thermostat should be fine though.