That "How to use a computer" ad is brilliant. I think Apple is really (finally) onto something with the iPad Pro (less so with the other iPads). The pencil, the keyboard and USB-C really solve almost all the things that limited the iPad. But if you buy all of those (iPad Pro + Pencil + Magic Keyboard) you're paying so much that you may really consider buying instead of a computer. A Wacom tablet, for example, still requires you to work at a desk, and its design and wireless capabilities are a joke at best (dongle, constant signal problems despite being right next to the dongle, excessive pen, tablet and nib wear, clunky, bulky, creaky plastic design, etc).
The iPad has, over the years, gone from a glorified iPod Touch that's just a reason to spend more money without really getting much for it, to a full-fledged new "thing" in its own right that can definitely do many things that you'd do with a computer better (being more portable, having an internet connection without WiFi, battery life, touch screen, responsiveness and low software maintenance needs), and then some things you can't even do with a computer (touchscreen and Pencil). I definitely get why so many people use the iPad Pro for their work. You can stand around and takes notes then and there, drawing things with the pencil onto a PDF, whatever, it's something you simply can't do any other way.