Bob, I nearly did but then it fell through. I sent details, lots of pictures etc and they came back with a sales price. They strongly indicated that this was a guaranteed minimum price so I agreed. They then put the car out to dealers who would bid on it. The best dealer offer was well below the supposed guaranteed price and so I pulled out.
Had they made it clear that the price they initially offer was not guaranteed then I may have seen it through but I took the hump with them over that, I thought that they hid that in the very small, small print. As long as you are aware that the price you get is only firmed up AFTER the dealers put their bids in that is fine.
The idea that they simply pick it up from you, transfer the money etc is very appealing and I believe works smoothly, if you get that far.