Well i follow the forum and read all the speculation about how good the mark iii would be... I almost cancelled my pre order based on the chatter. I have had a 5d mark ii for three years and shot a lot always raw generally iso 100 and avoided moving targets.
To me the mark iii isn't 1 or 2 stops better about its about 100% better, go take some pictures. I shot some really good candids today around Covent Garden in London, mainly because the camera was quiet and I can crank up the iso, so no flash and no noise to attract attention.
My real interest in Landscapes and until a dxo raw convertor arrives I wont know the difference in IQ or noise but I always shoot landscapes at iso 100.. (today I was shooting 2000 and the pictures are clean really clean). I do know that as I travel around I only need take one body now, so I save the weight of a 7D from my backpack, as previously i took a 5Dii and a 7D I will now get more candids and avoid the back pain, with the loss of some lens reach.
I really like the mark III, and if the criticism has been as wrong about most other aspects the IQ when the raw convertors get finished and tuned it will be awesome as well.
Yes I do wish it was cheaper and expect the price to drop and will feel the bump, but its taking good pictures.
Now if I can figure out how to magnify live view to focus my TSE accurately I will be really happy.
I know RTFM