There are so many things which look less lovely and are just as incongruous to the natural landscape - acres of hydroponic greenhouses, industrial estates, Ikea warehouses, cooling towers (although I like their cuddly shape!), any amount of heavy industrial processing plants like oil refineries, airports, multi-lane highways and grids, and, as Andy says, huge electric pylons, which look like cyborg armies marching aggressively across miles of fields. I think there's nothing more unattractive about the modern energy windmill than the old-fashioned flour grinding one - they're bigger, but neither is the old style unobtrusive. Both look rather serene when they're turning, I think, and remind us that, at least, a natural element is powering them.