Rob Galbraith did a great review of a preproduction Mark III.
The camera’s features may be difficult to sum up, but the camera’s performance isn’t. It’s awesome. Pixel-for-pixel, the image quality is the best we’ve seen from a digital SLR, and except for one preproduction body glitch, it’s also the best SLR we’ve ever shot with too. The EOS-1D Mark III shows a level of design care and engineering thoroughness that is simply unprecedented. Its list of features is impressive. But actually using the camera reveals how impressive all these features work.
There is a couple of full size sample images provided. The comparison between the Mark III and D2Xs files on high ISO (see page 3 of the review) show how big the blow will be to Nikon.
The Canon EOS 1d Mark III will hit the shelves in June.
On a side note, I did not know that Galbraith was Canadian. I was pretty surprised to see my home town University volleyball team featured in the sample files.