I checked out a building yesterday that had heating mats like this one installed in four areas. Obviously it's electrical resistance heat, and there's an attic above so there's doubtless some loss into the attic, but these definitely make you feel warm, because your head is so close to the heat source. There was 1260 watts of heating installed in this area, along with 576 watts of fluorescent tubes. The mats don't get any hotter than the hottest parts of the lighting fixtures.
Any comments on this type of heating?