I have mostly been using the Claude Sonnet models as they release each new one.

It is great for getting an overview on a pile of code that I'm not familiar with.

It has debugged some simple little problems I've had, eg, a complex regex isn't behaving so I'll give it the regex and a sample string and ask, "why isn't this matching" and it will figure out out.

I've used it only a little for writing new code. In those cases I will write the shell of a subroutine and a comment saying what the subroutine takes in and what it returns, then ask the LLM to fill in the body. Then I review it.

It has been useful for translating ancient perl scripts into something more modern, like python.