I entered some of the following in another thread, that started out with my questions about choice of 5D mkIII or 6D.
I ended up choosing 6D - and enjoy it much sofar.
I add some samples.
These first two are mainly test-shots. But they both show me lots of promises on what this camera can do.
It resolves and renders delicately (swan's feathers / water surface)
And it does quite a good job regarding focus (I tried a bit of BIF, which is not my regular domain).
Two last samples are some of my favourite motives. (They were entered a few days ago also under the Animals/ Birds-group here in CR.)
All four made using 70-200 mm f/4.0 L IS.
Also I noted that I can go HIGH in ISO - which gives me a lot more flexibility.
And the camera handles near to perfectly for me.
All in all: A giant step forward from my previous 450D / Rebel XSI.
Much more playing / testing / gaining experience to be done - love it.