People keep trying to rate real estate agents, mortgage brokers, lawyers, and other professionals. But I know of no online system that really does this well. The problem usually is that participation is too low. It is hard to draw a conclusion from just a couple entries. One negative review can skew things badly, as can a glowing review from an agent's close relative (or, dare I say it, from the agent himself/herself). If you are looking for a good agent, my best advice would be to ask people you trust for recommendations. Then interview the most recommended agents carefully and insist on an escape clause in the agreement you sign so that you can terminate the contract early if things do not work out.
Best, Ron Rovtar
Berkshire Hathaway HomeServices/Real Estate of the Rockies
gedfuly campBoulder, CO
zillow gives out badges to agents that perform upto their standards. The only reason I am aware of it is because I just recieved one from zillow and I am ranked up there with other performing agents. I hope this helps.