Although I am *ahem* a little older than a college student, I think that many have the same reactions that I do. For pleasure reading and browsing, an ebook or online reading is great (even preferable). But for actual studying, the print copy works best. Having the tactile experience of physically highlighting or flagging something with a post it creates a sense-memory that I just don’t get with an ereader.
The emphasis in technology has been on getting the ereader to “disappear” as you become lost in the story. To consciously learn, retain, and be introduced to new ideas can be an uncomfortable process. This, coupled with usually less-than-stellar writing makes it very difficult for a textbook to disappear.