Whether you use the program directly with a dealer participating in the program or indirectly without identifying the dealer, I've found this part of the program useful. There's an analogy to Priceline where you get some information about the seller but don't necessarily get all of the information early in the process. In 2009, I used this service to research cars within a 200-mile radius of my home in Virginia. I saw a number of options, including several dealers clearly within the Baltimore area. I didn't attempt to set up anything through Amex; I just realized that the lowest price in Baltimore was several thousands less than in my home area. It was worth the effort to go to Baltimore and negotiate with the dealer I suspected was the dealer in the Amex program.
When the time to start talking dollars arrived, I just pulled the sheet from my folder and said, "I don't know if this is your dealership. But I do know that I can get this price by hitting the Send button and getting American Express to identify the dealership. If this isn't the dealership, it probably doesn't make any difference to you, except that if you can't match the price, I'll be walking out of here, knowing that I've narrowed the list of remaining dealerships that will offer this price. And if I've picked the right dealership, I've just saved you the percentage you'll have to pay American Express for sending my business your way."
I got the price within 10 minutes. Could I have done better? I'm sure I could have saved several hundred dollars more. But could I have had an easier purchase? No, because I'm sure I had the right dealership in hand, and they knew I was right. They would have lost several hundred on the sale if I'd actually asked Amex to identify the dealership I could have negotiated with, in turn forcing the dealership to pay Amex a "finder's fee."
The caveat: I negotiated in June 2009, just before the Cash for Clunkers program was formally announced. I figured that once the general public knew that many could get thousands for their worthless trade-ins, the dealers would simply up their prices by the amounts of the anticipated rebates. And since the dealer I used had a website with their published, discount prices, I was able to check several weeks later, after the Clunkers program was announced, to see that the price for the car I had bought had risen by $2000.