Yes, I could have shopped around for a used 5DII and opted to not do so. I feel the 6D is about 90% of the 5DIII in the features that are important to me. I get the latest full frame sensor, image processing and high ISO handling for excellent image quality. I generally shoot relatively stationary targets, so the faster AF of the 5DIII, while totally sweet and desirable, was not worth paying a great deal more for me. I'm not a big video shooter, so the faster video capture of the 5DIII was not a huge draw for me. Another card slot would be nice, but again, not a problem for me. Plus I get wifi and gps which are not built in to the 5DIII.
Considering my admittedly not demanding needs and current product price points, I am happy with my 6D. Full frame goodness.
That said, if you found a great price on used 5DIII, it is a better camera.