As I have stated many times, and I think most folks agree, if you are not printing really large you just don't need this many pixels, particularly if making the pixels smaller degrades image quality.
Having said that, I am constantly impressed with what wonderful technology has been brought to bear to have cameras that work really well at pixel dimensions we would not have dreamed possible only two or three years earlier.
Although I am primarily a Nikon shooter, I used a 5D with great success for several years with my Contax and Leica R glass. I finally gave up, not because of any flaws in the 5D but rather that I got sick of stop down metering etc.
So now Canon has virtually doubled the pixel count and one could hardly see any features whereby they went backwards in terms of functionality or quality. Yes the AF is not the modern state of the art but it is no worse than the current 5D. And other features are at least as good as the old 5D and the other features such as pixel count is a clear step upward.
As always, the proof of the pudding is in the eating. The only way to judge the image quality of the Mark II is to take pictures and see. It won't take long, using a first rate lens, to determine if the sensor is not in the league of the 1DSMkIII. If not, the 5D has been rushed to market to take on the losses being incurred by the presence of the D700, and sales will simply plummet.
We'll see
Just my thoughts
Woody