I got a few days ago my so long desired 6D. After some very few tests what I have noticed with regard to my former 450D is the much greater capability to fine focus. I have decent lenses (the ones I most use are the 24-105 f4 IS L and the 70-200 f4 IS L) and with my former camera I wondered many times if the investment on these lenses was really worth because the results I got were not according to what everybody told me that I should expect from them (L class and bla, bla bla). I even thought on going to Canon to check if something was wrong with them. Let's note that I always focus automatically and never manually (it takes too much time, I need my glasses to fine tune focusing, etc...). What I can say without any shadow of doubt is that the 6D focuses much, much better than the 450D, and that only for this it is worth to go from the 450D to the 6D. It is not a question of a few more megapixels, it is a question of faster and much more accurate focusing capability.