For my studies, it would have been ok until the final theses really - typewriting the text, analyzing statistical data without excel and drawing the graphs manually... wow! Hats off to those who really have done it like this before advent of PCs!
For the work... I think that lack of e-mail would be the most material change, it would be hard to imagine having to call and fax about everything.
Life in general it would be fine, as I value my friends above all anyhow, and seriously like other media like reading, cinema, good TV series on DVD - but booking travel without Internet would be a pity though.
However, had I played Baldur's Gate before losing my computer though, I sure would miss good RPGs!