My motto is, don't give good feedback unless they diserve it...
I have no problem giving neutral feedback if the person wasn't a good ebayer but I still received the product.
I give bad feed back if the product was not as advertised, I didn't receive it, or something else went horribly wrong.
I returned an amp I got off ebay because the guy put a photo of a similar model in mint condition...said it was in mint condition, but when I received it, it was scratched to all hell, missing mounting screws, and had broken feet. I only gave him neutral feedback though because he was very cooperative with the return.