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Good technique, in my humble opinion, is needed with all cameras, regardless of number of pixels. Defects in technique tend to be amplified regardless of the number of megapixels.
When the D200 was introduced I remember many photographers stating that they needed "better lenses" since 10 megapixels were demanding on optics. I used a D200 with my new and old lenses and I never saw files that did not show the quality of even my cheap lenses. For me it is a habit to photograph from a tripod and if I use hand held techniques I make sure I am shooting at a high enough shutter speed or I use VR lenses.
The D800 is not going to be different in that respect from a D200.
No matter what camera or lens is in use if we want to have quality we need to do our part.