Light weight. The ability to focus (with center point) and take clean pictures (high ISO performance) in the dark enables me to take pictures that I was never able to with 5D mark ii. Good ergonomics. In-camera lens correction. Wifi and connection to smartphone.
Delete button is hard to press with right thumb when holding the camera with right hand. No pop-up flash. Focus points clustered in the middle area. Focus point selection can be awkward even using the multi-way controller.
Great light weight camera. A huge upgrade from 5D mark ii. Love every aspects of it except for some issues with the focus points selection methods.