I read at the JESEL site that shaft rockers replace: studs, stud girdles, stud rockers and pushrod guideplates.

What advantages do shaft rockers have over regular rockers?

What would a typical shaft rocker setup be like?
I imagine it consists of a long base that is bolted into the holes where the rocker studs would be and then the shaft rockers mounted to that base. Is this correct?

Any comments on shaft rockers?