Ian and I decided to use the Silverlight Chat a week ago and the conversation went kinda funny. There were long pauses and each person made comments that seemed out of place. After awhile one of us asked the other, "Did you get every message I sent you?".
The chat has a log and we each looked at it and realized that more than half of the conversation was missing! Turns out that any message more than 100 characters was not being sent. It was an easy fix and the latest one is deployed at this link, but had we not used it we would have not found the bug. In testing we always tested using short messages.
At my work we recently started to use ADefHelpDesk. On the first day a number of small bugs popped up. They were small, like a misspelling on a notification email, but they are the sort of thing that still makes a difference. We just did a release with a fix for all the bugs that we discovered yesterday.
Now that I will see ADefHelpDesk used everyday in a large site with hundreds of users, we will be able to discover any bugs and performance issues first hand and fix them immediately. This should provide a better product for everyone.