Nikon D800: The best sensor on DxOMark
andThe Nikon D800: A full-frame sensor with no weak points
D800 rocks...Portrait: 25.3 bits (tied for 3rd, best full-frame score, very close to the best medium-format scores)
http://www.dxomark.com/index.php/Publications/DxOMark-Reviews/Nikon-D800-Review/Sensor-performance