Especially for new software in a different language than you already know or haven't used years, in a realm other than your current area of expertise. It's pretty useful to be able to directly ask it how do to, eg basic string manipulation in $new_language, but even more convenient is to ask it to do the transformation for you. "Given a string of the format X, write a $language snippet that outputs X'." It'll do more advanced things than that, but that's one area I found it to be useful and time-saving in an unfamiliar language because it saves me from looking up that boilerplate before getting to the part where I throw a regexp at the problem.