I have yet to have a bad experience buying anything on eBay, and I've bought dozens of items, including the hardware for several computers and loads of musical instruments and studio gear. You've got to do your research and check seller ratings carefully. If a seller has a couple thousand positive ratings and only a very few negatives (usually in the single digits) that's a pretty darn good risk, in my opinion.
Only time I got burned on eBay was when a high bidder didn't follow through on something I was selling.