Yea, I mean everyone has gripes about their job. It's just part of being a working man/woman. Sometimes you just have to smile and nod your head. I mean I work in customer service. My top three gripes would be:
1) Customers who insist that they know more about your job or an item than you do.
2) Customers who pick stuff up to buy and then change their minds and leave it someplace random (or their trash for that matter).
3) Customers who are rude and talk on their phone while you check them out and then get annoyed when you have to ask a question.