Most of the key specs are substantially upgraded compared to the 5D Mark II. The new sensor, coupled with Canon’s latest DIGIC 5+ processor, offers a standard ISO range of 100 - 25,600 that’s expandable to 50 - 102,800. An 8-channel sensor readout enables continuous shooting at 6 fps. The shutter is rated to 150,000 cycles and has been refined for quieter operation; the Mark III also inherits the ‘silent’ shutter mode previously seen on the 1D-series (which delays mirror return for more discreet operation). Viewfinder coverage is a full 100%, and the 1040k dot, 3:2 aspect ratio 3.2” LCD screen has improved anti-reflection properties and a hardened glass cover to protect against scratching. And let’s not forget that 61-point focus system from the 1DX - the first time Canon has put its top-spec AF sensor into a non-1-series camera since the film-era EOS 3
A quick look over the specs shows that the Nikon D800 is still king of the megapixels (36 vs 22), but the price is about the same as the the D800 ($3500ish). Overall it looks like a nice upgrade for Canon folks, though I doubt that Nikon users will be jumping over for this (ditto for Canon users jumping for the D800). Interesting to hear what the guys on the Digital Convergence Podcast have to say about it!