Honestly if I could just print up a new tablet instantly and without cost, I would have half a dozen around me when I am deep into a research fugue.
Being able to quickly and easily flip between books or articles (or even different sections of the same book) while at the same time keeping the existing information up on a screen that I can directly reference is great.
Maybe people are setting it up at home using a numberpad? In that case it would be just running a finger down the left side.