I agree with everyone, you can tell immediately by the way they answer the phone. If they sound like they can't be bothered to be there than it's time to "grab another line" and call back later. You can tell who wants to be there and who doesn't. I wish they would have someone who does nothing but listen all day to these calls. I know sometimes it says your call may be monitored but I doubt that happens in any kind of quantity.
Many years ago I was watching some 20/20 type show and they were interviewing the president of some company who listens to customer service calls all day long. They run in the background instead of music and he said he has fired more than one person for being incompedent or rude. I would love to see more companies do that. You know we've alled talked to people (airline or otherwise) who had they had a supervisor listening would no longer be working there.