My buddy and I have each bought cars from eBay twice this past year (02 SLK, 03 Audi, 95 E320, 91 Taurus). We believe we got good deals this way. Each was a positive experience. Each car was either almost new or had relatively low miles. Both my cars were from Florida, where there is a HUGE market for good used cars. I understand your feeling of buying sight unseen. You may want to limit yourself to low mileage cars.
It is all important to check out the seller's pedigree, that is, their buyer feedback rating. The successful ones sell lots of cars to happy buyers. Some of the sellers are small time used car dealers that find eBay a good venue to sell specialty cars they bought from auction houses to a wide market, rather than just in their local area. Many lease cars are traded this way.
Some buyers pay to have the car shipped. Others fly down to pick it up and drive home. Some arrange their vacations around their purchase where they fly down and use the car to drive around Florida, California, or wherever they are.
95 E320 Cabriolet, 131K