I've bought two airplanes with certified checks from the bank. I'm much more comfortable with that than toting around thousands of dollars, especially with the police's occasional propensity for robbing people. It comes down to what people are comfortable with, and yes a quick call to the buyer's bank should clear anything up. Safer and easier than cash, IMO. As a buyer, I would be annoyed (and slightly insulted) at a seller insisting on cash, but it would not break the deal.
Matt
Matt