The windmills are what made me choose the Cape for my seaside house search as opposed to some other beach community on the northeastern coast. I have lived in sight of windmills in CA and ME and they are absolutely beautiful to see, all lined up in a long white row, spinning lazily and creating clean energy. Way better than living next door to a coal plant (or downwind from one) or a nuke plant.
Nantucket has not been completely immune to the national home market decline. I don't belive any of this decline is due to the threatened windmills. If and when they are erected, and the hundreds of strobe lights and fog horns kick in, there may well be some price erosion. I love windmills, but not in Nantucket Sound.
Not as of yet. Although there are certainly many questioned being asked. It's such a gray area at this stage it's hard to tell what impact this will have on Real Estate. Certainly I wish for greener alternatives for our energy resources, but I do believe there are better places for something with such a visual distraction.