I've bought probably 10 or 15 things off ebay, had 2 bad expierences. One was arguably my fault, I hand wrote a letter to send with my money order with my address, and he sent to 705 East 12th rather than 205 East 12th, when the guy at 705 East got it he refused to accept it and it got returned to the seller. The seller then did not want to resend to me OR even refund the money. After some arguing and legal threats (interstate commerce, which I'm sure wouldn't have held up) I got my money back. That was for a stereo reciever.
The only other time I got screwed was when I paid about $6 for a NES game and when I got it it didn't work, luckily though I had bid on that game in another auction and "accidentally" won that one, and the game worked. So I wasn't too upset.
I've also gotten at least 1 pretty good deal. I bought a surround sound decoder for my 5.1 ready reciever for $5, in perfect condition, the only thing it was missing is a remote, and I think I can work around that by using the reciever's remote (both same brand). I haven't hooked it up yet. The only downer to that was it cost $17 shipping, but I still came out ahead by quite a bit.