I'm curious about professionals who do actually productive work on a tablet or even phone format. The touch screen or color calibration can be helpful, but you could probably use the money spent on an iPad in getting those extra features for your desktop or laptop. If you are a remote worker on the move, having a mobile setup would be well worth it and perhaps your only option, but the experience of getting any work done seems so woeful.
A lot of film work is done on set and mobility is important. Currently high end productions who'll use DIT (digital imaging technician) carts which quickly become unwieldly. While this one replace all those setups, in certain scenarios where you need to be mobile and fast (branded docs, smaller crews, etc) a smaller highly mobile setup becomes ideal.