People might get annoyed or offended, but I think this needs to be said (don't smite me, please). If you are or wish to be a full-frame shooter and really, truly, heartfully can look at the spec list for this new camera and say with a straight face, "wow, Canon REALLY missed the mark on this one. The D800 is going to crush this!" then I feel confident encouraging you to go buy Nikon equipment, because constantly switching is going to be the only way for you to find happiness in this world. You could try getting a pet, too. Like a gerbil.
I made a post a week ago that I now would like to retract, claiming that the 5D III was in trouble if the price point was really $3,500 compared the D800's $3,000. Given the spec list here and the sheer refined look of this camera, I think it easily justifies the extra $200 or $300 in actual market price over the D800. EASILY.
For the individual claiming that this is just not enough resolution and you need 38 for your wedding photography, you're not going to find a lot of friends over at Nikon, given that they only had 12 megapixel sensors for, like, a millennia, and did just fine. I'd like to take a moment to remind you that in the 1990s, wedding photographers shot with a medium called "film" with 45 autofocus points. If you can honestly look me in the eye and tell me with a straight face that your photographs look bad or in any way insufficient at 21 or 22 megapixels, I will do you the courtesy of looking you back in the eye and telling you bluntly that it's not your camera that sucks, it's you. I will than buy your 5D Mark II from you and give you a pat on the back. It's going to be okay.
I had no plans to upgrade from my 5D Mark II, but this camera is making me rethink that given that it didn't just upgrade one or two things, but everything, including the body lines (still waiting on dimensions and weight). This tells me that Canon has generated a golden seller. If this thing weighs less and is smaller than the Mark II, I'm advising the wife the credit card bill is going bulge this coming August. Autumn landscapes, here we come... Again, no smiting, please. This is to be a day of joy and happiness.