there is buyer protection, from ebay and paypal, so better than a local used item. The low feedback amount is a little off putting, i have not had any problems with items off ebay yet. I purchased a used 7970 before the prices dropped for crossfire, from a person who had under 25 feedback, but good reviews, and was all good.
I would contact the seller thru ebay, and if he replies fairly quickly, then a good chance he is reputable, at least to a point lol