Miners use no more electricity than an electric heater. 100% of the electrical energy "used" by the miner is converted to thermal energy (heat). Of course in most places there are more cost effective methods of heating a house such as natural gas furnace, propane, or heat pump.
True, and as you say, the electricity draw is only equivalent (well, for the most part) to a space heater in terms of "heating" up a space (in fact, I think a website did a study on this).
If there was a way of having multiple sources of heat through mining (having small miners embedded in different locations with fans circulating the heat, or some sort of schematic like that), and the system's electricity draw is at (or just marginally more) than the electricity draw of one of those houses with the more efficient electric heating systems, that'd be awesome.