This is interesting. I am fully supportive of e-books, but my experience of textbooks on my I-phone were slightly mixed. I think that is just because it's in the early stages.
For me, overall, though, the pros absolutely outweighed the cons and I will still buy e-textbook all the way.
Of course, this is just my experience. Other students may feel differently. But here's what I loved and didn't love about them:
I loved (!!!) carrying them to class in my pocket. I loved being able to read them anywhere, anytime. I loved that I could buy them and have them in 3 minutes.
I loved whipping out my little I-phone in class, while everyone else clunked their huge texts on their little desks. I got several "oooos" and "ahhhhhs", and one professor told me "good job." One of our texts was over 400 pages! And I love that they are easily accessible after class. Some of the books are classics, and I'll need them at work.
There was a downside, though. The main one is page numbers. If I want to quote a text in a paper, most of my e-textbooks didn't have the actual pape number attached. Amazon was working on that though. Halfway through the quarter there was an update that gave page numbers to one of my books.
Also, the highlight function doesn't work well at all on the I-phone app. Probably does work on the Kindle, Nook and I-Pad, though.
Some students may feels it's a downside that they can't re-sell e-books after the end of the quarter.
So, I think it's slightly mixed, at least it was for me, but I imagine all the glitches will get hammered out very soon.
Of all the factors involved, not having to carry huge texts around will be the deciding factor, imho.