I agee with Bitt: if your house is well insulated, and you are using a radiant heat solution, then it will definitively be cheaper to just set it at a constant temperature and forget it than to switch it on and off all the time. The energy needed to re-heat the cooled off mass of the house is enormous.

This of course does not apply if you have a non-brick, badly insulated and heated by forced air systems/radiators house.