does the regex search for what you wanted to? Does it work in all cases? Can I be confident that it will find all instances i care about, or will I still have to comb the code manually?

If you find yourself writing regexes often enough that speeding up that process would increase your productivity by "a lot", then you should get good at writing them yourself which means practicing without an LLM. If its something that you don't do often enough to warrant getting good at then the productivity increase is negligible.

I think the main benefit here isn't really productivity but developer comfort by saving them from having to step out of their comfort zone.