Good reps are on time with their deliverables, within budget and are professional. They also have good reporting skills. A good rep is one who is a good listener and provides me with what I want on time. They follow up, but are not too pushy. They give me time to get back to them.
Good reps are ones with quick turn-around time.
They provide flexibility in the RFP to allow you to pick and choose from a menu of options. You don't have to buy the crap to get the good stuff. Good reps do not try to get too involved. They stay on track and don't try to weasel their way into other businesses. Good reps are straightforward.