I have completed almost 150 transactions on eBay, almost all of them purchases. I had one problem in all of that, the rest were great.
Rules to get benefit out of eBay:
1. Know the actual value of what you're buying and don't pay more. Be prepared to walk away from any auction that goes above your max price and don't get caught up in 'win fever'.
2. If something sounds too good to be true, it is. Don't be a jackass, then run crying to mama.
3. Pay your debts, be polite, and don't think for a moment that just because you're doing something over the internet that it is somehow less real.