I just registered so I could reply to some people who are bashing those who are questioning the "awesomeness" of the 5DIII. Especially if someone actually bought a 5DIII and is reporting their opinions of it and they aren't up to the glowing standards others have.
There's nothing wrong with trying to know exactly what you're getting for your money.
Currently I have two 5DII's. If I sold one for $1600, and bought a 5DIII for $3500, that's a difference of $1900.
So what do I get for that that I would actually need/use?
Autofocus sounds better by most posters, but a couple have said that in low light it still hunts and will refuse to focus.
Viewfinder sounds better, so that's cool.
Dual card slots I'm not so interested in, but maybe it's a feature I could learn to appreciate.
Now image quality is the big one. I shoot a mix of studio fashion/headshots and weddings/events. Currently when doing low light work, I like the image quality up to ISO 1600. If the 5DIII can make ISO 3200 files that look as good as my ISO 1600 files, that's a winner.
I haven't seen any reviews showing this though. Not with RAW files. I've only seen JPG comparisons, which is meaningless to the professional who shoots RAW.
I think everyone will agree that this camera is an upgrade. The only question is if it's worth the price to upgrade from the 5DII. I the image quality doesn't meet my expectations, I'll probably buy another low light prime lens, and wait for the price to come down before jumping in.