Well, as a Chicago resident, when I have to fly I usually am on Southwest, normally with Chicago-based crews. The customer service on Southwest is top notch every time I fly with them.In the case of Chicago it almost seems to be cultural identity at this point. United Airlines is based there and features service that is on par with Amtrak. None of the places I've visited in Chicago ever struck me as friendly and some were overtly rude. I've been backed-off (lesser form of trespassed) exactly three times in my life and two times were in Chicago, so maybe it just goes with the territory, so to speak.
Of course, in the end, all our experiences are anecdotal. My recent long distance (coach) Amtrak trips from Chicago have been on the Lake Shore Limited, and the crews have been perfectly fine.