I've sold about 30+ items on ebay and have bought 40+ items. Due to the same buyer buying on multiple auctions, which only 1 feedback counts(83/83 positive), I have a rating of 77 with 100% positives.
What Richard talks about is important. Provide as many pictures as you can and be as descriptive as you can. I refuse to bid on anything that has shady detail or I can't see in advance, unless the seller is willing to send a picture.
Checking feedback is important, and I make sure to check it for about any auction. I've only had one transaction that went 'bad' from the seller's end, and i just chalk it up to the guy didn't follow through on his end of the deal. I left him no feedback in order to not risk him leaving me poor feedback, even though I paid him promptly and did my part. Sometimes you have to suck it up
I know a lot of people who have gotten screwed by people on Ebay, but it has become less of an issue since Ebay and Paypal teamed up and Ebay has added more buyer protection. - AB