When I read e-books on my computer screen, I almost always use 2-page view (it just feels natural to display them that way), but I didn't like the 2-column mode on the Sony 900. I think it's the vertical:horizontal ratio of the columns. They're not the rectangular shape that my brain expects; I felt like I was reading a folded paper, and I had the desperate, uncontrollable urge to somehow unfold it. Maybe that's just part of my weirdly-wired dyslexic brain, but it was a distracting and uncomfortable way for me to read.
That said, I'm all for anything that allows users to customize their reading experience to best suit them. You should contact firstname.lastname@example.org
) with a suggestion to add a two-colum display option - it could be a new justification selection.