Justin Blanton hasn’t gone iPad-only or iPad-mostly, but rather has moved almost all of his work to his iPhone:
Much of what makes this possible is that I can delegate in one way or another most of what I think of, and can get away with being extremely terse in my emails. At this stage of my career my day-to-day job requires minimal work-product; if I was coding all day, designing websites, or researching, I probably wouldn’t be able to leverage my pocket computer the way I do, but I wouldn’t want to either.
At my day job, I see so many people obsess over what kind of computer they have, what the specs are, and the idea that for even basic tasks, some sort of “upgrade” (more RAM, an Intel Core i7 processor) is a necessity because they are a “power user” of some sort. However, they’re not doing some sort of heavy data processing, software development, graphics/media work, or all the other traditionally power-hungry tasks, but rather email, some document manipulation, and web browsing. Furthermore, when out of their offices, they often supplement their computer with their phone for most of these tasks. For most people, the current crop of iOS devices are plenty of computer for most tasks. Besides that, for most people that would rather focus on the tasks at hand, there’s often less that can go wrong or fuss with on mobile operating systems in general.