Interesting read over at TeleRead on whether reading e-books could harm your eyes. The good news: according to a doctor who was asked by the person writing the article, reading e-books (from a backlit device) does not harm your eyes as long as you don't read in a "totally dark room". So all you Sony Reader, iRex iLiad, HanLin, Starebook etc. geeks using an external light source, you should be fine. The bad news: My eye sight has definitely deteriorated over time, and I don't know what else to blame but the e-book.
Link to full article