FWIW, I bought my pickup from Mossy Ford about five years ago and had a very good experience. They post the prices on the window with all the rebates and discounts. There was no negotiation on price, it was a take it or leave it. It was a 28k list price, end of model year (October) and the price shown was just over 20k. After agreeing to that price, they tried to sell me an extended warranty, which I declined. I was going to pay cash, but they offered me another 2k rebate if I would take out a loan and not pay it off for 4 months. In the end I got the truck for just over 18k, plus tax. Then paid about 250 in interest during those four months, and paid off the loan after that, so that was a pretty good deal.
I suppose if you are a really good negotiator, you could get a better deal at another dealer, but from my shopping around, I doubt I would have gotten 8-10k off from another dealer, so the set price model is way better for me. Not sure if they are still doing that or not though. It was over five years ago now.