It's true that e-books are still horrible for some types of books. I'm currently abroad using a travel guide on my B&N Nook and it's impossible to toggle between a description of something on one page and a map showing where it is on a different page. With an old fashioned book, it would take a second to retrieve the desired data by sticking one finger on the page with the map and another on the page of the description.
I think I would have problems retaining info if using an e-book version of a textbook, but then again, I'm old enough to have purchased vinyl and cassettes. Perhaps younger folks who have grown up with an LCD inches from their faces at all times will have no problems.