The Sony a7R won Popular Photography's Camera of the Year in 2013, and for good reason. It's full frame sensor is the largest available with no anti-aliasing filter for remarkable image sharpness. I love mine but it took quite a while to unlock the true power of this camera.
First of all, it has so many customizable features that it would be impossible to put them all onto the camera's controls. The Sony a7R even allows you to download apps from the Sony application store to customize the camera even more.
Features like eye auto-focus, face recognition and tracking are not accessible under the standard camera setup. Yet these features are so powerful that experienced wouldn't even imagine such features even exist. But they do!
Unfortunately the manual isn't of much help and there are practically no resources in showing how to apply these stunning engineering innovations to your photography.