I just got off a call with a perfectly lovely fellow who had absolutely no clue. He said that I was very good at my job. I was able to answer all his questions and explain everything in ways he could readily understand. I went the extra mile for this person, because he was pleasant and in a good mood. It was a good call.
I mention it here because in our jobs, and in this thread, we have a tendency to complain and vent. We tend to focus on the bad customers. I think it's important for our outlook and sanity to recognise that occasionally, we get good ones too.