I can agree with the skeptics that LLM generated code is usually crap. I rarely accept its output without significant edits unless it's truly boilerplate, and I want to avoid the need for that kind of code in the first place.

For me, the killer use case is debugging. I hate wasting time debugging something that should work except for mistakes, and now I do that probably 75% less than I used to because AI does it for me.

I don't know if it makes me that much more productive, but I certainly enjoy my work more not having to do as much tedious debugging, and it feels like I waste a lot less time doing it.