By holding with one hand do you mean to carry around? I am sure that you shoot with both hands on the camera. Even on a tripod I rest my hand on the lens unless I am using a remote trigger.
I have not noticed any inconviences in the D800 vs my D90. But it is heavier and bigger. Many folks with large hands also say that the grip makes a big differnce for them in handling, especially vertically.
Dan (Nikon D800,V2,Sony HX400V,Lumix ZS40) "I don't read, I just look at pictures" - Andy Warhol