been a while since I used it, but it was handy for templates where you need to enter a name once and have it typed in multiple places in the template (quicker than a find/replace). It was a also handy sometimes to just be able to put your cursor on the name of a variable or bigger text selection, smash cmd+d a handful of times to add another cursor at every other occurrences of it in the file, and then just start typing to modify each of those occurrences.