Locutusx, a friend of mine goes into car negotiations with his own thorough spreadsheet on his laptop so that he can plug in numbers and come up with real figures before the salesperson most of the time. It certainly leaves no room for confusion when seeing what features, payment plans, leases, finances, etc. affect what. Just another way to be up-front, honest and quick in the dealership. More up-front prep work on the consumers' part, means less time wasted in the dealership for them and the dealer staff.
Hell for me last time, I went in, drove the cars I was interested in (after months of research... well, it's pretty much constant when you're on here anyway) and after plugging all their "best offer" prices into my own spreadsheet at home, called the salesperson up, made my best offer... it was accepted, I went in that night and signed the papers. Nice n' easy on everyone's part. (now actually getting my car to arrive with snow tires for delivery... that was another story!).