Like Scott, I've taken many rides in the Jump Seat, but I don't hold any pilot licenses, so each time I take a FAM I ask questions. Some of the questions I ask most often are:
1. How slow can you fly on final with everything hanging out.
2. How fast can you fly on final with everything hanging out.
3. What are your climb and decent rates best and average.
4. How quickly can you slow when given a speed reduction, level flight and during the decent.
5. In an emergency how can I best help you.
Being an approach controller I'm working hard to vector you around, over, and under other arrivals, departures, and over flights, as well as trying to establish and maintain a final. When I ask for a speed reduction, I need it now, not 5 minutes from now.
Safety is a team effort.
Mike