Bruce, I've been active on eBay since late 1999 and majority of my transactions have been great. Sure, there have been few bad apples, but overall I'm quite happy with my eBay experience.
I mostly buy, but I've also sold some things.
Funny, I recently did the same thing - overcharged for shipping. I enclosed a dollar bill with the model and had a very happy buyer on the other end of the transcation. Sometimes little things make a big difference...
Peteski