Pretty much; I figure everyone works in retail at some point, so you'll know what customer service is like - a real pleasure sometimes, just part of the job you try and do as best you can most of the time, and an excuse for people to treat you like utter dogshit the rest of the time.
Closing down sales are ROUGH. People actually laugh in your face, openly insult you and start fights. Fortunately we had a good security team and management had officially stopped giving a fuck.
You start to lose your customer service attitude FAST, you're on edge anyway due to the whole no-job, my beautiful shop looks like a bomb went off thing. You start to concentrate on doing what you can for 'actual' customers and the abilty to cater to the desires of the vultures diminishes fast.
If it wasn't closing down sale, of course I'd have just smiled and checked the lady though like any other customer, shrugged a bit inside at the shame of a high-demand item (at the time) not going to someone who'd get good use out of it.
I worked in a massive, inner-city store, obv that has an affect on the type of people who came in.