...and the fact I haven't been to either place, the German location did not come off well as Martha's Vineyard. Besides knowing that Polanski couldn't film it in the States, there are other indefinable qualities about the setting that made me realize it had to be someplace quite different than the Vineyard.
I grew up on Cape Cod and have been to MV many times. I can say that the beach scenes were passable enough. Their modern, minimalist house, however, was very unusual and I don't think I've ever come across anything like that on MV. Not saying there couldn't be houses like that, just I've never personally seen one. Most houses in Cape Cod tend to stick to modest, traditional designs and since the islands (MV, Nantucket) are smaller, the building regulations are even stricter. People remain pretty traditional over there.
The street scenes were also passable, although not quite exactly like MV...they looked more South Shore to me. That said, as someone who grew up in that area and who didn't know it was a Polanski film before seeing it, I thought they managed to capture the atmosphere and the likeliness of New England pretty well. I'm not sure what kind of image Cape Cod has for folks abroad but I think many people might be disappointed when they come here and see that many parts of it are rather bleak and ordinary. It's not flashy like the Hamptons. Discretion/modesty is the operating mode over here, regardless of how ridiculously wealthy you may be.
Did you enjoy the film?
I had read the book in one sitting, not because I thought it was great, but because it was an easy read. I liked it enough though. Aside from the ending, the film followed the book faithfully, even with some of the dialogue. I ended up enjoying them both.