We now have access to Proquest Historical Newspapers (well, the NY Times), and I am deeply thankful. I've spent some time just running searches to see what a thing of beauty it is.
However, it doesn't have everything. I had used the old paper versions of the Reader's Guide and Book Review Digest to locate a review of a book by Obscure Author a few months back and, having found one in the New York Times, looked it up on microfilm. It's not available in the Historical Newspapers collection, though.
The Historical Newspapers project is a real godsend, and I'm grateful for it. The work is done in India, to ensure accuracy (as I read in Business Week* at the gym this morning), and it's clearly a huge undertaking. I guess my point is really a plea to librarians: electronic resources aren't perfect, so please keep paper resources whenever possible so that we can cross-check them with the electronic ones.
*Our gym has the dullest magazines on the planet--this was the most interesting one I could find, which tells you something.