Samples are here
Image portfolio in the latter complements the former.
Astonishing image quality samples undisputably far better than the MkII, sheer joy to have such power at hand for the price, over and above the term "enthusiast's level", I'm glad they didn't fall for the megapixel race, I'm ordering one before they change their mind and give us back the MkII!
Some note from Planet5D and their hands on and comparing the 5D3 to the 1Dx:
The stills we were shown were significantly better than the 5D2 – the noise levels were reduced and at the higher ISOs the color was better. The Canon EOS-1D X is even better still. It has 1 stop better but the pixels are also a bit larger because the Canon EOS-1D X is only 18mp.
Said this over the past 2 weeks that the 1Dx would have the better IQ. 5D3 looks better than the 5D2, but there was no way on God's Green Earth that Canon was going to let the 5D3 surpass the 1Dx in IQ.