The WSJ profiles some university pilot programs that replace conventional textbooks with e-book readers, such as the Sony Reader. The article gives the impression that results were about mixed, at best. So many students are used to video and other supplemental online content that the e-books seem antiquated relative to a similarly sized netbook. But in general, it seems like many students were happy enough to be rid of their textbooks. It looks like the question will be what device students end up using, rather than print vs. digital.
For me, I like reading linear stories on the Kindle and it would probably be wonderful for English majors that want to highlight lots of text and add annotations, but it has some major problems displaying equations properly - as in, sometimes it just puts up wierd squiggley marks rather than the numbers you should see - and isn't so great for flipping around, even with the search features. The good news is that technology is constantly improving.