A lot of these responses are from the standpoint of the seller. I wonder what the responses would be if the OP had said he just BOUGHT a car on eBay? Would folks be recommending that he send a cashiers check and be OK until it clears the bank before the seller sends the car? I would also expect that a real, legitimate buyer would want assurances too. If they don't, that is as much of a warning flag as anything else...
I think the key thing here is to find a responsible transaction between buyer and seller that protects both. Yes, cash in person works, but it is a pain in the butt for large dollar cars and travel is not always possible. Plus, it's not easy getting $20,000 or more in cash, and not fun either to transport it, handle it, etc. And yes, cash too can be forged, although this is pretty hard.
I know nothing about escrow accounts through eBay, but I would bet that have been designed to protect both buyers and sellers. If you use one of those services, know how they work and be sure they protect you appropriately.
Hope it all goes well!