My colleague and I recently conducted one-on-one usability tests over several days for an internal project. The tests were very productive and revealed findings that helped our client make some informed design decisions.
During the week, we had many "quotable quotes" from the participants. One of my favorites was the following helpful tip: "You know what you should do? You should talk to a bunch of different people about how they would use this, because everyone is going to have a different perspective."
Say...wish we had thought of that!