I go to the website and submit the feedback with the flight # and date/time along with departure/arrival just in case. I try to get the name(s) of the crew as well.
Not sure if AA ever really responds (it's been a while since I had good feedback for AA--haha).
I know UA and DL have replied back after some time letting me know (not the automated one, but a real composed email) that they've forwarded onto the appropriate people.