One of the limitations of shooting entirely from the camera is the size of the rear LCD. It's perfectly adequate for many situations, but once I'm trying to judge critical focus, styling, expression or small details, a larger screen becomes considerably more useful.
Traditionally, that meant setting up a laptop. For a commercial studio shoot that's often still exactly what I'd do, but it also introduces another computer, a stand, power, cables and additional equipment into the shooting space.
Using the iPad gives me a useful middle ground. I retain a much larger review display than the camera while keeping the physical setup relatively compact.
My workflow perspective
I don't see the iPad as a universal replacement for a computer-based Capture One station. The value is having another option. For smaller shoots, location work and situations where portability matters, that option can be extremely useful.
Workflow 01
Portraits
Review expression, focus and styling on a larger screen without surrounding the subject with a full tether station.
Workflow 02
Location
Keep the capture setup relatively compact when carrying and repositioning equipment matters.
Workflow 03
Clients
Give a client or collaborator a clearer view of incoming photographs than the rear camera screen provides.
Workflow 04
Products
Check composition, placement and small image details more clearly while the shoot is happening.