Just another quick anecdote as to why AS customer service is excellent:
I missed a flight this AM because I had an urgent situation that involved buying a walkup fare on United yesterday. I forgot to cancel my AS ticket.
AS was under no obligation to provide any sort of refund or credit because this was purely my fault for breaking the fare rules - AND I was flying on one of their competitors. But nonetheless, they issued a discount code for the value of my ticket which is more than they needed to do.
(and the converse to this story is also true - United's customer service once again disappointed)