The crisp seams on the recent plastic versions are kind of jarring to those who know the sensual rolled edges on the original metal versions. The limitations of the metal forming processes actually added to the unified beauty of the original. It was ironic to touch a cool feeling metal housing to turn down the heat. One would expect the device to feel too warm if the room was too warm. Now, it's ironic to touch a warm-feeling plastic housing to turn up the heat.
Setting aside that newer designs can vastly improve conservation of fuel, there is something to be said for intuitive designs like this one. But I've often wondered why they never made it easier to read; many models had silver numerals on a silver background.
Beyond aesthetic sensibility, presenting the temperature on a semicircular, rather than straight line, gives visual emphasis to the middle area of the range. Although it is subtle, contemporary designers might consider this graphic emphasis in guiding user behavior, particularly in the context of energy-consuming devices.