I've sometimes talked about mobile writing, as I have a fondness for writing in cafés. And generally I consider the lightest gear to be the most desirable for this, like a Macbook Air or an iPad Mini with a USB keyboard.
But: there's something to say for the no-compromise approach. And this fellow likes his screen real estate, so durnit, he brings his 27-inch iMac with him! There's no stopping him, he can do 3D graphics work, web design, photoshopping, you name it. Rock on.