Mh, I don't really. There are few things that need to be changed all at once. The only recent time I needed regex on a wider scale was when I botched org-mode radio targets after a recent syntax change, which was a simple case of replacing >> with >>> and << with <<< respectively, as well as extracting some text from within square parenteses and put it on its own instead. But 1 to 2 lines of sed -i are not thaaat challenging! ;)
That poster probably meant things such as quantitative text analyis, comparing language patterns used in literature, etc - which is mostly a question of interpretation, but requires some skills in scripting for the initial data gathering.
