The Economist has interviewed Paul Courant, librarian at University of Michigan, on the subject and the impact for research to have, at least, all orphan books digitized and searchable. One of the points he makes is that the book project gives different universities access to each other's libraries digitally, for the benefit of research. But as he also points out, Google is not doing this only to be nice, but rather to get more eyeballs to browse their webpages and adverts.
They have recently given On Demand Books access to their digital library to print books for customers. This posts interesting questions to how other actors in the digital/physical distribution of books should react. Even though the currest deal with On Demand Books only covers orphan book, books without rights holders, it is most likely that it at some point also will cover books with rights holders.