I primarily use it for C++ in Unreal Engine and use it almost exclusively to write log statements. The way to log something is done via a macro like so:
UE_LOG(LogCategory, Warning, TEXT("My variable: %s"), *SomeStringVar)
Writing that boilerplate soup gets tiresome after a while, so having Copilot autocomplete the log statement for me based on other statements in the same file and the context of the function is godsend.
It does of course happen that the text contents are wrong, but then I have that skeleton to work with. Just erase the text and type the correct contents I want. Saves so much time.