In theory this question applies to other brands beside Canon, but I'm going by the Canon experience here. Namely:
Why would I want to change a functional focusing screen with another one? And what is a 'super-precision' focusing screen? It's a silly name; it's not like we have imprecision by default. What are we getting, here, and losing (other than cash) by swapping the screens?
I have a recent body (6D), and I read about different focusing screen options (if I recall, three options from the settings). I never hear about these things in reviews, etc. All I know is that the focusing screen is interchangeable.
Do I care? If so, why?