A few days with my 5D3, big improvement from my 7D. The big test was taking photos of my son play hockey. Hockey is tough because most rinks have bad lighting and the action is fast. Focusing is better and I took photos up to 10,000 ISO and they were just great. With the 7D at 1600 they were not as good. I wish I could of had a camera like this 5 years ago. Of course the reach of the lens is not as great, but I found even after cropping the pictures are still much much better. Shutter sound is different, I think I like the sound of the 7D more, for what it is worth. Transition to 5D3 was seamless. For those who have the budget a must buy in my books.