I only ever had one problem on ebay. Sadly it was over an Elbox tower from Germany. The seller told me he was having problems getting it posted to me as it was an "oversized" parcel. After nearly a year of being quite resonable and patient with him I threatened legal proceedings (and yes, I meant it).
Got the tower within a week after that.
I've sold loads on ebay myself and have 100% positive feedback. Other members of this forum (eg. Phantom) have had dealings with me and I'd be glad to see a good/bad buyer/seller list as save2600 has mentioned. I know the side of the list I would be on.
PS. I'm 258graham on ebay, just so ya'know.