I currently own a 60D and like it for what it is. I have been wanting to step up to FF and right now, the 6D is the only option in my budget. I recently found a good deal on a 6D body and took the plunge.
My reason for the 6D was the improved low-light capability, and the overall benefits of a FF sensor. I do shoot sports occasionally (soccer), and will continue to use the 60D for that.
After having it for a few days, however, I have to say I'm not that impressed with the images, compared to my 60D. Using the same lens (EF 28-105, yes an older lens) on both, the images from the 60D are much crisper and sharper. The images from the 6D are very soft, to the point that it appears the camera is not focusing properly.
I've read very good reviews of the 6D, so I'm pretty surprised at my results. I am nowhere near a professional photographer, but have been shooting for a long time as a hobbyist/amateur. I was extremely excited to get the 6D, but am wondering if it's an issue with the camera, if there are tweaks that need to be made, or if my expectations were too high. It's extremely noticeable when viewing images at 100%, which the examples below don't convey. I don't normally pixel peep, but the first images off the camera were so soft, it got me to comparing the two at 100% and the differences were very obvious to me.
A couple images attached, same lens (EF 28-105/3.5-4.5), same focus point, straight out of each camera, shooting RAW. No PP has been done. First image is from the 6D, second from the 60D.