My dad bought a car off ebay a few years ago. The transaction went very smoothly. We are on LI and the car was in Kansas City, MO. The seller was a used car salesman so im not sure if that is what made it so smooth, but either way it was pleasant.
All the funds were transfered before we even saw the car(in person). Insurance, registration was also completed. We flew out there slapped on tha plates and drove home. The seller was very nice too. Picked us up at the airport and even bought us lunch. That impressed me.
I guess i am just used to the hustle bustle and assholes of the metro area. This guy seemed very honest. The car also never failed on us. So based on my experience, i would do it again. But ours may have been unique.