I presume it varies greatly based on your area and task.
If you are slapping together a thin generic webui over a milquetoast sql database in a boilerplate-heavy language/framework, then sure I could see massive speedups.
In my particular area, the most unobtrusively useful enhancement is letting it take a crack at a 'code review' before I push it for real. One time it did catch something that would have gone unnoticed that wouldn't have come up for a long time and then it would have been annoying. However earlier today it started going nuts highlighting code that I hadn't changed and insisting that all the variables were named 'dict' and that was a bad idea and should be renamed. Nothing was named dict, the word dict didn't even appear in the codebase it was looking at.
If getting started on something unfamiliar, I *might* do a prompt and then reference that for things to potentially look up. I first started trying to do that and fixing up the result, but ultimately decided that outcome from prompt was harder to salvage than to just throw out and maybe use it as a reference.
I have had moderately more success in letting it predict the next few lines, though it often gets very opinionated about something very wrong. It also tends to assume incorrect things about interfaces that I deal with, interfaces that *should* have been verbatim in their training material.