One thing we've learned from the (relatively) new field of behavioral economics is that people tend to remember the pain towards the end of something, not the total pain. Thus if a painful surgery ends with a long period of less pain we remember the experience as being much better (less painful) than if the pain maximizes towards the end. (Footnote: Daniel Kahneman's TED talk)
I had a hunch this was true. I've always felt it was important to make sure that a user's experience at a helpdesk ended on a good note. Even if the user is reporting a disaster (data loss, etc.) or if the experience just didn't go well (we mis-handled the request), I wanted the last bit to be a period of reduced pain.
Some ways to do this: hand holding, conforting, chatting with the person to "talk them off the ledge", or just an extra email to them saying, "By the way, I'm really glad you reported this problem. We weren't monitoring for that particular condition but now we are. As a result, our monitoring system is one step better and this will help everyone in the organization in the future. Thank you!"
Yes, it may sound a bit cheesy, but it is true and authentic.
We often forget that people are often intimidated by the thought of opening a helpdesk request. Doing simple things like that helps keep the communication channels open.
P.S. If you are near the NJ/NY/PA area, I'll be speaking at the LOPSA NJ PICC conference, May 7-8, 2010 in New Brunswick, New Jersey. For more info: http://picconf.org