I had a complete nightmare once, involving four european flights followed by a late evening flight to Nairobi on the same day. I was so impressed with the CSD on the last flight (who really looked after me seeing how half-dead I was) that I wrote a comment letter. As I didn't know who to send it to, I just sent it to the top :-)
I got a personally signed reply from Rod Eddington thanking me for my kind comments and assuring me that the commendations would be posted to the relevant people.