By way of one example, displays such as this and the Wacom Cintiq are great for graphic artists and and the like.
As a Tablet developer I like displays like this too. Connected to a desktop-grade system I can run the Tablet OS and have the benefit of the built-in digitizer to help me through debugging. I did much of my early dev work this way. I’ve been 100% Tablet-bound for my development the last couple years (I like developing on the platform that users will be using), but I’ve thought about picking up a new 21″ Cintiq and a loaded desktop system for some of my bigger projects. So far the cost–and the bulk–have persuaded me not too.
The one drawback with built-in digitizers over external ones? The hand can get in the way. Oh, and up till now they’ve been more expensive. With companies, such as Samsung, entering the landscape, this may be changing.