I just wanted to let you know how much I appreciated the work of your employee, David Webb.  He was very responsive last week when I called with a leaking water heater problem.  David was altogether quick, thorough and neat in his work.  He was friendly and had a great positive attitude.  The leaking water heater problem was indeed a bummer, of course, but I couldn't have asked for a nicer or more skilled person to replace it.  David represents your company well.  
Sincerely,