The New York Times has a very interesting collection of opinion pieces on the subject from a wide array of professional "readers".
From the skeptic:
"Right now, networked digital media do a poor job of balancing focal and peripheral attention. We swing between two kinds of bad reading. We suffer tunnel vision, as when reading a single page, paragraph, or even “keyword in context” without an organized sense of the whole. Or we suffer marginal distraction, as when feeds or blogrolls in the margin of a blog let the whole blogosphere in." - Alan Liu chairman and professor of English at the University of California, Santa Barbara
To the advocate:
"The tools (as usual) are neutral. It’s up to us to insist that onscreen reading enhance, not replace, traditional book reading. It’s up to us to remember that the medium is not the message; that the meaning and music of the words is what matters, not the glitzy vehicle they arrive in." - David Gelernter, professor of computer science at Yale University
It is an excellent read and offers 5 different points of view, each eloquently presented. Worth a read.