I've been buying on Ebay for 5 years (not all that much over the last 2 or 3 though) and have been selling a few.
I've never been disappointed with my purchases (one wasn't as well presented as described .. but as it was a 1/4oz gold kangaroo and I only paid $110 for it I wasn't too put out!)
In selling, I had 1 problem with someone in Germany, but it all just came down to words, not money lost.
However, I am very careful as to who I buy from, and place great store in a reliable feedback history. These days I only buy from Australia (was more adventurous when I started) since if I get really browned off I can actually go and visit the 'problem'.
I'm not dangerous at all, but nobody but me and you knows that.