That depends on the person.
Personally I do not like to make any demands other than to say a particular issue is unacceptable.
Many times I just provide feedback to ensure that someone at Qantas knows there are issues and I am hoping they are logged somewhere in the system. In a lot of the cases I get a call back to discuss the issue such as premium check-in (or lack thereof), delayed luggage, on time performance, seat allocations etc. I have been sent vouchers and I have also been sent bottles of wine simply for providing feedback. Or they felt sorry for me.
When it comes to IFE though that is a different story. IFE not working is unacceptable and I want some sort of compensation but I am not going to include that in the feedback letter. I want to see what is offered first before proceeding further. And I have not been disappointed so far with what has been offered....