this boggled me before when I was still shooting with a D700
i think its averaging the values of the house and the sky.
SO FAR i have noticed that the F6's meter seems to be almost always spot-on
its smart enough to pick the human in the scene and meter from it/them.
havent shot snow yet but they said that the F6 and F5 meters can recognize a snowy scene.
what i do now is if i suspect my camera exposing for the sky i will just do spot and then average the scene myself. i am used to using a separate spot meter and its second nature to me.
i am not sure if this is just NEF file specific though...
Nikons film cameras metering seems to be really accurate for most situations EXCEPT scenes with lamps and lanterns because the camera will consider them in the metering too. for this, spot metering is indispensible