My opinion has not weakened over time but rather has strengthened. That column came out before the current hype about e-book companies, services, and devices, so I simply focused on the retrospective conversion problem. But there are also clearly places where they do fit and are increasingly likely to replace print books.
Any book aimed at students is prime territory for an e-book.
When I was a student, I lugged some 50 pounds of textbooks from class to class. For students, e-books are clear winners. One slim device is all that's required to put dozens of titles at your fingertips, along with annotation capabilities, easy dictionary look-ups, etc. The problem is that libraries typically don't purchase textbooks. Nonetheless, just about any nonfiction title, particularly those that are used in reference or quick look-up fashion, seem as appropriate as books.