YMMV but generally legitimate gripes will be met with some form of compensation. I've certainly let AA hear it when an issue within their control resulted in some significant inconvenience for me--I recall once a TPAC flight went MX and left me with a day's delay, and on another occasion an arrival got parked at a gate without deboarding for well over an hour because someone on ground ops had taken the jetway key home with them (it was the last arrival of the day). Both got 10k miles compensation, if I recall. Granted, I was EXP at the time, but I reckon if AA's bungles cost you a measurable chunk of your life, you'll probably be taken seriously; persistently complaining about the amount of ice in the drinks or weather delays wouldn't be a winning strategy.

[Aside--got a very puzzled response from a phone agent when I joked that my Helix score must've been pretty high after another cancellation followed closely on the heels of the TPAC mentioned above.]