"Reputable" is one of those loaded terms that probably isn't a good word choice, because all of the major brokers are reputable. They are all duly licensed and regulated by the State of Florida, and in fact, have to conform to exactly the same standards of ethical and professional conduct as Disney itself.
"Effective" is probably a different story, and each of us can only draw on our own experiences. I have bought and sold through The Timeshare Store, the long-time sponsor of these boards -- and have had amazing service from them. To me, they are the pros -- the standard the others try to match.
But all of the major players are certainly "reputable."
