When the Nikon D800 was announced, the specification that got everyone's attention was - and to a large degree still is - the massive pixel count of its 36.3MP CMOS sensor. When a moderately-sized full-frame DSLR body aspires to go toe-to-toe with medium format cameras and backs at a fraction of their price, other attributes can seem secondary, but 3, 1/2 years since Nikon released the D700 Nikon has updated much more than just the resolution. The D800 has a significantly more advanced feature set than its predecessor, particularly in terms of its video capabilities that make it, on paper at least, a viable and tempting option for professionals.
Nikon users coming from the D700 will feel largely at home with the D800, but where changes have been made they (usually) have the effect of improving the shooting experience compared to the older model. Of course, the game changer is that you now have 36MP at your disposal, a resolution that was, until the D800 announcement, the sole province of very expensive medium format cameras/backs. The D800 does indeed offer a level of fine detail that ranks it among the best performers we've subjected to our studio testing.