Nikon's D800 is the Best Ever Analyzed by DxOMarkThe folks at DxO are intense about cameras and sensors, scoring the quality of a camera across a variety of categories and assigning scores based on rigid tests. When they say that the Nikon D800 sensor is the best they've seen, that's well worth paying attention to.
The D800, as DxOMark puts it, is "A full-frame sensor with no weak points." The RAW sensor results put the camera at the very top of DxOMark's list, beating out more expensive models and every other new camera on the market.
Keep in mind, of course, that these scores are based on image quality and nothing else - flexibility, ease of use and other concerns aren't accounted for.