What a little marketing all can do. Nview isn't that much more advanced than twinview. The limitation of twinview was that the second head supported only 1280x1024 and not higher. With nview those problems are fixed the second ramdac runs at the same speed as the first ramdac. (350 MHz)
Next to this there are no hardware changes. Perhaps nvidia made some software changed on Windows to let people think it is something new.