In eBay's defense, I've completed over 400 transactions buying and selling and only had two bad experiences. One the buyer didn't pay so I sold to the next lowest bidder. The second the seller was a drop shipper and the item had been discontinued. It took three months to finally get my money back. 99.95% success rate is pretty darn good so eBay is still my favorite place to buy/sell things.
Brucelee - One thing you can try if the seller has a regular website is filing a complaint with the Better Business Bureau. You can also mention it to Square Trade if they are a member. I did those two things in addition to the eBay and PayPal routes. I was too late for the eBay and PayPal reconcilliation (make sure you start the complaints within 45 days to get your money back) but after getting several complaints from the BBB and Square Trade following up, the seller finally refunded my money.
As mentioned earlier, eBay is just like an online classified. Just as the local paper cannot possibly check out every person advertising in their classifieds, eBay can't do it either but they do have the feedback system to help out some if you know how to use it. Don't just take a 99% good feedback rating as nothing will happen. Read through the seller's past week's feedback and see what happened. There are several drop shippers (like the one I delt with) who get 200+ feedback's per day so even with a few bad ones they still have a high feedback rating. This gives them the opportunity to ignore any problems, mostly because they are a nuisance with over 200 transactions per day and will go away without much complaint. It's buyer beware so if you're not comfortable with it, like Brucelee says, don't use it.
