Summary: I've been waiting a long time for a D4. I've rented them in the past and couldn't wait to actually own one. I purchased mine used with 34k actuations, 3 batteries, extra CF cards, original box and accessories. I was able to contact and speak to the owner and get more pictures of the condition and ask questions about it's history. This was instrumental in my decision to purchase used. It arrived a 10 out of 10 in perfect condition at 2/3rds the price of new.
Summary: This is a great camera, my issue is it came with a spot on the sensor that I just can't get rid of. From some reviews, it seems when they assemble them some get a oil residue on them that cannot be removed.
Summary: Even two years after it's release, this camera stands the test of time. It's a solid workhorse with fantastic low light image quality that feels and sounds as a pro camera should! Until... You have any issues with it and then it's all down hill if you are out of the warranty period. This was one of the first cameras released so maybe that's the the issue with my body. In any event, here's my story.
Summary: Given the price differences between the D800 and the D4, I was seriously upgrading from my D700 to the D800. I found from friends who have the D800 that the D800 is a wonderful landscape and studio camera with probably the best video capabilities of all Nikon cameras. However, the D800 is a bear to use for event and street photography. And forget about using it for sports.
Excerpt: I have the d4 for about a year now, I mostly shoot sports and action, and I love this body more and more Every time I use it. Great ergonomics , just fits like a glove in my hand , lighter than the d3s I used to own, high ISO amazing up to 12800 , and paired with my 400 2.8 vr and 200 f 2 vr ii , I have no problem getting those shutter speeds in low light. The autofocus simply amazing, and the overall camera a joy to use. Nikon did a great job with this body.
Excerpt: Firstly I am a Nikon user only. I read a lot about the D4 before I purchased. It is like the I have gone light years ahead (pardon pun) .The low light capability of this camera has changed my entire outlook when I think of composing a picture. No worries about tripods just bang up the ISO, such freedom and ability to express without penalty.
Summary: Yes, all the 4 and 5 star ratings are highly warranted in the previous reviews and this is a truly great camera. My problem with the D4 is that the two fastest consumer flash cards available are not compatible when used together in the camera. I spent the extra dime and purchased a Sony XQD S and card reader. A SanDisk UDMA 7 compact flash card came bundled together with my D4 purchase. Naturally, I put both cards in the camera right out of the box.