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Question: When moving it up and down there is a rattle that sounsds like a loose part in the flash head. Stops when you raise the flash.  Is this a defect?
Document: I compensated for it using Rockwell's published hint of adjusting the color balance.- There is an annoying rattle when the flash is closed, which is most of the time, and which stops when the flash is deployed. I guess that's normal, when the locking springs are not engaged.Overall, I'm very impressed. But, I add the final note that the new camera has also been a bit of a home wrecker.
The defect is I guess could be metering or something wrong with sensor. First it was not obviouse but wen I started to compare get  this with some of my point and shoot and Sony NEX 5n the full frame $2800 piece could not keep up with light performance and picture quality Yes that how bad it is. Example making a shot of 5pm sky with tree line in the lower part of comp.
I use my D 800 for hand-held macrophotography of tiny insects, which are typically in motion. The 36 megapixel resolution is helpful because my moving subjects are difficult to frame while I am photographing at 1:1 magnification. The high resolution enables me to use severe cropping later to correct awkwardly composed pictures. I use flash so that I can eliminate artifact due to subject motion and camera shake, and to maximize light for achieving high depth of field with low apertures and low ISO's.
I am returning my third D800 because of the widely reported bad left focus point. Unfortunately, Nikon is still (Sept 2012) producing defective cameras and has not fixed the problem. What is worse, when you call the company, like an ostrich,  they stick their head in the sand and say they have no info on the problem.Besides the poor quality control, the camera has wonderful ergonomics.
First of all. I want to say that this is my second DSLR. I went from an old Canon Rebel XTi to this. I was a Nikon film man back in the day (N50, N70, F100), but Canon was my first digital SLR. I waited 4 years to upgrade and it's like being in Back to the Future Part II, when Michael J. Fox gets his hover board.
At first it seemed the Nikon D800 might be too  demanding for an amateur like me, but once in my hands and utilizing my lens system, I was very encouraged at the results. This is the 'kitchen sink' of Nikon cameras. I feel as if I am only part way of the mountain of its versatility. Just learning each new possibility capturing excellent s***s is a wonderful adventure. I appreciate ordering David Busch's field guide to help me.
Our family went to an amusement part with our 3 year old daughter last week, and the AF noise wasn't as prevalent due to crowd/ride noise in the background. But like I said, I don't have an external mic yet, so I am not sure if that will aid in reducing the noise from the AF mechanisms.What an incredible camera. Coming from a D700, I would have to suggest upgrading to a D800 only if your finances allow.
Actually I'll be selling my Nikon lenses - they will be on Ebay soon-  and moving to Canon. Mark D5 III has been put on top for DSLRs on its range, besides Canon assumes publicly responsibilities and fixes any  problem that may arise- not like nikon that even refuses to acknowledge the problem, let alone fixing it.
I have owned an original D70 since it's introduction. While very happy with it at the time, I always dreamed of moving to a full frame sensor camera sometime in the future. I have held out this long waiting for a camera like the D800. Initially though I was going to buy the D4. Impossible as it may seem I did not know the D800 was coming out.
Coming from the D200 (which I loved) via the D300 (which I did not) it's a homely feel and all the buttons are where I want them to be. LiveView on this one is simple to use, unlike on the D300. The one thing I really like is that the focus point selector is far enough to the right to be out of your way while holding the camera. On the D200 I had to lock it to avoid moving the focus point with my nose.
Answer: $3,000.00 cameras are not maracas and should not sound like one when in motion. Clearly, there is a loose part somewhere. My advice? Return it. I have been using Nikon for over thirty years and after the D800 fiasco I will sell and move to the D5, with not much regret,  as Nikon's customer service and respect has really suffered.