Buying one from Apple is only 499. That means this deal is only fifty bucks cheaper but you don't get all the warranty and support coverage. Plus I am willing to bet ten million dollars that they are refurbs. You really want to buy someone else's problem? What is the return policy etc.? Not a great deal honestly. You will get burned by this. Just don't say that you weren't warned first.
First off, it is listed as brand new and factory sealed. Secondly, even if it was refurbished, all Apple refurbished products come with a one year standard warranty anyways, same as a new model. Thirdly, if you were to buy it from Apple.com, the price is 499 + tax. Depending on where you live, this can be an extra $50 or more. So you are saving at least $100 buying from eBay.
Apple does a great job refurbishing products, they are not sold unless they meet strict requirements. Or else they wouldn't give it a standard 1 year warranty, unlike a lot of other refurbished products out there.