Nothwest Airlines ruled the roost for arrogance while I was a near-weekly air traveler. I've heard Delta has inherited this tendency.
I used to think the customer service barometer was driven by airline, but now I of a mind that it is driven mostly by location. USAirways, for example, in Pittsburgh (when it hubbed there) was helpful, but Philly? Assholes.
Northwest out of PWM, friendly. Detroit? Hostile, dishonest, lazy.