This guy used to write pretty good articles, but this one is egocentric nonsense. I don't personally use an iPad for work much either, but I edit video and photos, and make music on one - all three of those tasks I prefer to do on my iPad.
When Joel Spolsky was starting out I agreed with at least four out of five things he said and the fifth was more of a “huh?” As time went on quite a few “no, Joel” and a few “yikes” reactions began. He petered out when I still thought half of his stuff was good. I’m sure others have kept going.