I haven't experimented with a standing desk, but it seems like you can develop a tolerance overtime, so that eventually, you'll stop thinking about the discomfort when you're trying to concentrate. I can see where the author is coming from though. I tried to read a book when I was cycling in the gym, but it didn't go so well because I ended up spliting my concentration with the book and exercise. No gains in either activity unless I sacrificed the other. However, standing is a low-intensity physical activity, more similar to walking, so I think that overtime you'd just get used to it. It becomes a healthy active habit like taking the stairs everyday.
