I use it for more "OCR Nightmare" than grammar nightmare. Here's a (trimmed) example:

#Please clean up the following text:

Ile took an active part i•all the proceedings of the day. All went expecting to have a grand, good time, and none were disap- :~ ~ii~!c~,rcwT~:a~i~~c~ 0

'J farewell set, and Mr. Bailey 1·eturncd the
~ :d~~~~ls!i~s/;;r;rie\~
11
i~:n~~Ut:sa~~i°:::
[: tended to them a cordial invitation to meet
,o him at that place on the 25th of August,
['. 1877. And echo said "So m]fii! b8;~n .
..

#ChatGPT

Here's the cleaned-up version of the text:

He took an active part in all the proceedings of the day. All went expecting to have a grand, good time, and none were disappointed. The merry company engaged in a farewell set, and Mr. Bailey returned the warmth of their farewell. He extended to them a cordial invitation to meet him at that place on the 25th of August, And echo said, "So many have been."

That was from a scanned 1800s newspaper. Adobe Acrobat did not do a good job converting it to words. ChatGPT cleaned it up nicely and kept about the same meaning. There were some swings and misses, but it's much easier to edit the result into accuracy than the original mess.

#Actual text as hand-transcribed:

He took an active part in all the proceedings of the day. All went expecting to have a grand, good time, and none were disappointed. The mirth continued till the night drew near, when they danced the farewell set, and Mr. Bailey returned the company his hearty thanks for this renewed expression of their friendship, and extended to them a cordial invitation to meet him at that place on the 25th of August, 1877. And echo said ``So mote it be.''