I've made three complaints lately - all of them were justified in my opinion. Other than that I've never made a complaint in all of my flying with them - I'm usually pretty happy - just not lately.
The first one, I got a sorry you don't like our new standby policy (which I don't because it's impossible to standby for later flights unless you do it at the airport) but we think it's a great thing.
The other two, I heard nothing - one was a combo on the half baked upgrade they did on a sold out flight which caused completed chaos and a late pushback and what the GA made the poor flight attendent go through because they had an empty seat in F and didn't upgrade anyone into it (although the FA made a comment on how many plats were still in coach). The second was about what's up with the elite preboarding in DTW - why do they cancel it all the time due to large numbers but on my return flight they manage to let us preboard even when there are the same large number of elites?
Wonder if you send a lot of "gee you guys are great" comments, you can get off the complaint list?