Having spent a goodly portion of my life in libraries, both as a patron and a library employee, I am aware that there are a lot of things about seeing books on shelves and having them to read that are lost when the books are digitized. The greatest loss is the synergy of having books grouped together. No catalog or index can give you the perspective of reading the shelves, that is, looking at each book in turn about a particular subject. Whatever the limitations of the Dewey Decimal System of cataloging books, the system did put the books into subject groupings that lead me to find interesting items I may otherwise have missed. While at the University, I used to spend my lunch hour walking up and down the shelves looking for anything interesting. No matter how good Google or other search engines become, that experience, of seeing the actual books and randomly looking at their content, is lost in the digital world.
My experiences at the Family History Library in Salt Lake City, or any other genealogy library have been the same; I find more information that is unplanned and unanticipated by simply looking at each and every book in a subject heading. For example, looking at all the books on Massachusetts genealogy in the Family History Library. This activity of looking at each book may take a lot of time, but it is the one sure way not to miss something important. Its not that I don't trust catalogers, they do an adequate job, but they don't know what I am looking for. I am really glad that libraries will not go away completely during my lifetime.
Availability is an issue. There are certainly more books in the Family History Archive or on Google Books than I will ever look at in my lifetime, but relying solely on electronic catalogs and then giving up the search is losing the battle before it begins. The search needs to go to the actual books as long as they are still available.
Some researchers are so focused on minutia that they cannot see the trees for the forest. They think that if their surname is not in the book's index, then the book has nothing to offer and discard the book for another source. I find almost none of the researchers at the Mesa Regional Family History Center even look at the books for the state where their relatives lived. They come and go from the Center without even knowing that the books exist right there on the shelves.
Computers are great for answering some kinds of questions, but if you want a general background about a subject, you need a broader look. I read books on my computer and on my iPhone, but having a book in hand lends itself to jumping around and using the book as it was intended, not just reading it from front to back for the experience of doing so.
Take advantage of the availability of books before they disappear from the earth. They have a lot to offer.