Summary: This is not a product that I purchased casually. Much research must be done to see if this camera is a match for you. There are plenty of reviews around, so I won't go into all the pros and cons for why you should or shouldn't buy this. I was back and forth between this and the D600, but ended up picking this because everything about it was on a more professional level. The quality of the images is unsurpassed if shooting properly.
Summary: I used Nikon cameras back in the "film days" - for reasons, I went to "another brand" and contemplated coming back into the Nikon fold for some time. My work is mainly photojournalistic and event shooting requiring work in all light levels. I find that the Nikon lenses are far better than other products covering the same focal lengths. I am shooting with a D800, D600 and D300 coupled with Nikon lenses.
Summary: D800 is performs great. It is heavy, so carrying around at locations, events, etc can be cumbersome. Especially with the Nikon heavies 24-70, 70-200. But picture quality is excellent. Response in low light conditions great. Working with off camera flash has been very good. Control over exposure is excellent. However I do not understand why two different format memory cards. I would prefer 2 CF or 2 SD. This is an addition to my D700.
Summary: I am a enthusiast, not a professional , but the amazing images that come out of this box are amazing, I am a business owner, but I will be moonlighting as a photographer because that's the insparation this camera gave me...AWESOME NIKON!!!
Summary: The D800 makes you use your A game to get good images. It is very sensitive to shake and requires a very stable setting or higher shutter speed to get sharp shots. If you get it right the image is amazingly sharp. The hype about high ISO low noise is not true in my opinion. If you need a camera that can shoot in low light without a f/2.8 lens use the D700. The D800 reminds me of my old D300 regarding ISO/noise.
Summary: I am not an expert; photography is not my trade / career - I am a very happy amateur consumer, as after I made the decision to purchase the D800 - I was absolutely convinced I made a profound right choice.
Summary: First, I started out with a Nikon D300 in college and then wanted full frame and went canon. Since then I have gone back in forth with Canon and Pentax, but something just wasn't right. I started reading reviews and it was filling my life. I then started looking at images on flickr shot with a Nikon D800 and I was just humbled looking at the images. There were amazing. So, I made the switch and since then have regretted ever switching.
Excerpt: Pros : - At the moment I believe this is the best DSLR ever. Simply. ALL things are great inside this beast except for minor complaints (see cons). - Killer raw files (dynamic range headroom, color, sharpness, fine details even after a strong denoising...). It is possible to recover almost ANY error. Cons : - Occasional sky banding in jpgs. Raw is often needed (I shoot raw+jpg).