Canon 5DIII a big disappointment for half the photo community and too expensive for everyone.
There are two photo camps that have somewhat divergent needs. They break roughly into the low light action shooters and the high resolution tripod shooters. Neither is right or wrong, just different needs for different types of photography. For low light, video, and action photogs, the improvements represent a desirable upgrade, at an undesirable price point. For high resolution, still work (and yes, there are plenty of pros that print big) the lack of resolution and perhaps dynamic range improvements are disappointing, to say the least. A previous poster said it right, the improvements amount to a 5D2.1 Most perplexing is the price point, particularly after Nikon released a much better speced camera for less. Unless Canon comes out soon with a high spec followup, they will have lost two sales here, one to the guy that buys my 5D2 and one to my new D800.
Canon 5D III is a minor upgrade for a major price. If you do a lot of video or shoot stills in the dark, the improvements may be worth the price. On the other hand, if architectural, fashion, or landscape photography are your bag, there's little here of interest. Given that the improvements center on video options, auto focus, and (I'm assuming) a stop or so improvement in image noise, I see little to differentiate the new model from the old for a large segment of still photographers. And yes, many photographers print 24x36 and up. I often push my 5DII to the limit. Here's hoping Canon has another card up its sleeve; otherwise Canon will have lost two sales, one to the person who gets a deal my 5DII and the other to a new Nikon D800E.
Canon 5DII, The Sequel... Yawn
More than 3 years after the Mark II and they came up with this? I would consider this a minor upgrade with improved auto focus and video. At $3500, it's overpriced and under developed! The 5DII broke new ground by combining a high resolution, clean sensor for stills with full frame video, for $2700. The 5DIII is like most sequels, a rehash of the old formula with a few new twists. The full frame video made a big splash the first time around, so Canon's logic appears to be "let's do more the of the same." While it's nice to have video on a still camera, if I'm serious about video, I get out a dedicated video camera which is superior (for video) to the handling of a DSLR in almost every respect. What Canon seems to have forgotten are the upgrades for still photography. There's simply very little here I see to justify an upgrade, especially for the price. Perhaps they have another card up their sleeve, but for now, Nikon has eaten their lunch.