I've had mixed results, but would still buy a car from Ebay again. Most of my problems have been from being impatient and buying vehicles that I should have passed by.

What I've bought:

1982 Volkswagen Rabbit TD. - Timing belt bad, neither me or seller was aware of this, and car died catastrophically.

1980 Mercedes 240D. - Car itself was excellent except for huge appetite for oil.

1975 Mercedes 240D. - Seller sold as project car, and he wasn't kidding.

1980 Mercedes 240D. - Rough looking, but ran great. Threw harmonic balancer a couple of months later, and died.

2000 Daewoo Lanos SX. Almost brand new car, and by far the best Ebay find I've ever seen and snatched up.

With anything Ebay, buyer should always beware, look at seller feedback, and try to go look at the car if at all possible.