I asked GPT-4 something fairly niche that I happen to know a fair amount about: to explain the concept of Xenon poisoning in a nuclear reactor. Other than skipping Te-135 being the initial fission product that starts the decay chain (and tbf, operationally it can be skipped since the half-life is 19 seconds), it got everything correct.

I'm sure if I kept probing on smaller and smaller details it would eventually fail, but I'd argue for _most_ people, on _most_ subjects, it performs incredibly well.