I think the best use cases of iPad are basically bifurcated into:

1) Consumption device People reading, scrolling, watching videos. Nice on the sofa, in bed, whatever. Also this use case has a lot of older users driven by eyesight issues that make a bigger slightly further screen interface better. Also very intuitive to young children (funny how often this elderly/youth overlap rears its head).

2) Creative (not productivity/coding!) device Artists needing pencil & touch interface for precise tactile writing/drawing/editing