Ebay impulse buy now seller wants out

Honestly I would like to know how binding the contract was. I understand they can just back out and it is up to me to ruin their feedback. Otherwise there is nothing legally binding....If I bought it and then backed out I am sure it would just ruin my Ebay ratings. The seller had been around since 2004 with 100% feedback so that is part of the reason I both bought the car and backed out of it without causing a fuss. Actually their ratings were very similar to mine.