Yes I knew about the dust issues before purchasing my D600. It's price, features and image quality set it apart from others.
With my other body, shot with it for 3 years and never cleaned its sensor. I never find myself swapping lenses frequently, I also shoot portraits more than anything else. If I see spots in any of my photos, I will blow it out.
This is my second D600, and I haven't found any spots, and I never saw any spots in my first D600 as well, and I prolly shot 2k exposures with it.