I just got the D800 camera and am very glad I have it.  One thing I’ve discovered is: although it use DX lenses, it shows the images reduced and the corners are blurred.  I don’t have many FX lenses but the images are worth the sacrifices.
   The viewfinder shows the full image has been reduced and can be set to automatic crop when you use a DX lens.
   Below is a copy of the first photo I took with the D810.  You will notice the cropping with DX lens.  I used a 18-300 Nikon lens and used the Auto-Crop setting which detect a DX lens.
   I guess in the future I may be trading my DX lenses for FX lenses.