This article, published in 1996, discusses how using the "World Wide Web" in the classroom can provide multiple historical perspectives and access to thousands of primary source documents. The downsides? The speed of downloading and finding quality websites.
It's true that students "are stuck" when reading a hardcover textbook. If they get to a word they don't know or a concept they don't understand, they are not likely to explore or look it up. I like the idea that digital textbooks could help build knowledge and curiousity, knowing that it's so easy for students to explore that second at their fingertips.