The Camera is as good as you have been reading but there are some new items to get used to.
1. Because of the enormous increase resolution and density range the camera needs to be handled more carefully then some of the lower megapixel cameras. Hand holding slow shutter speeds will show up as degraded images. Make sure you shoot on a mono-pod or tripod if shutter speeds are low. I tried to keep my shutter speed at least two times the focal length. Auto ISO is another great way to make sure your shutter speed is not too low.
2. Lens selection is imperative! there are recommendation by Nikon to which lenses are the best. Even with the best lenses it pays to know how to calibrate your lenses to your camera which you can find in the manual. Nikon provides an online digital tutorial at http://www.nikondigitutor.com/eng/d800/index.html which will help you familiarize yourself with the camera.
3. It would also be appropriate to see if your focus points are calibrated properly from Nikon. Initially the D800 had some AF problems because of the bad machine on the production line. It is fairly easy to find out if you have this problem or not. Do a search for checking the left AF point for accuracy. Here's one http://photokaz.com/2012/07/nikon-d800-contrast-and-phase-detect-autofocus-testing/ there are many others. I found that it doesn't have to be this complex. If there is a problem you could send it to Nikon but probably the best approach is to return to the dealer and get another one. If it's one of the new batches this should be fixed.
Good luck and be prepared to be surprised by the quality of these files.
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