Source:Paper beats computer screens
"People comprehend what they're reading on a sheet of paper far better than when they read those same words on a computer screen."[...] "A new Norwegian study of 10th graders confirms that reading texts in print versus on a computer screen is better for some aspects of comprehension. It was carried out by Anne Mangen and her colleagues at the Reading Centre of the University of Stavanger." [...] "The teens were then asked to answer questions that would show how well they had comprehended the text. The results clearly demonstrated that those who had read on computer screens had understood less than those who read on paper."
I know about cases where city councils have bought iPads for their members in order to save expenses related to printing massive amounts of documents, but in light of light of this research it's not certain that this approach is a good idea in the long run.