There probably are some people using it in the studio, but among the notable features of the 645Z (and the 645D before it) are that it's weather sealed, and shoots in landscape format. So I'd say it's aimed more at field use than in the studio.

Still very happy with my K3 (Mark 1) for its combination of ergonimics, durability and image quality. (Of course, you wouldn't want to use it for video. Picking horses for courses.)