Not arguing either way, but it is conceivable that reading comprehension (which is not stellar in general) can get even worse. Saving time for the same quality would be a positive. Saving time for a different quality might depend on the use-case. For a rough summary of a novel it might be ok, for a legal/medical use, might literally kill you.

"Positive impact" for me would be things like improve social injustice, reduce poverty, reduce CO2 emissions, etc. Not saying that it's a negative impact to make programmers more productive, but it's not like ChatGPT is saving the world.