mortoncc,
I am an agent and I don't know a lot about Redfin, except for the fact that they hire Real Estate Agents as employees of Redfin, of which when you sign up for their service, they assign you an employee to work on your behalf and you get some sort of "Rebate" depending on how much service you want them to provide for you...
I don't know the level of your experience with selling Real Estate, however I would assume you are a well informed consumer. My experience thus far has showed me that agents who can't quite make a business out of Real Estate (they are not good prospectors, negotiators, good follow-up, go-getters) would want to join a company like Redfin so that leads can get handed to them... is that the kind of person you would want negotiating on the biggest financial transaction in your life?
In life, I have learned... you tend to get what you pay for. The promise of receiving money back for using their service doesn't mean that the agent/employee did not negotiate the extra $30,000 or $50,000 you should have received from your home by using a proven Real Estate Professional, who is working on a commission basis, and is out in the market working daily to earn clients business, based on their ability to bring them top dollar, regardless of the market...
Hope that helps!