Serious question (I asked because my spouse is starting to have some of these issues) - if you can read a PDF on the iPad, how is that different from reading the HTML docs on the iPad? Is it something with the layout, or is it the cognitive load of having to click a lot of links rather than having a linear layout of the text? I'm interested in learning more about this to help my spouse out!

I get the feeling Adobe spends a lot of time making PDF work very well for reading. Different kerning maybe?

I have the problem that even an iPad is a tiring for reading even with the ability to position it in a more comfortable reading position than a monitor. I need to print stuff out and html truly sucks for printing. I can use e-ink and that seems fine which isn't an option either. Bandwidth is still not universal or cheap.