I've been on EBay since 1996. I'm a collector, and I've bought many, many items on Ebay. I now sell more than I buy, since I'm downsizing, but it's still one of my sources anytime I need an item. For instance, my DD needed a graphing calculator for high school algebra. I checked Amazon for review and prices, then started watching auctions on Ebay. In the meantime, Target put the one I wanted on sale, the price was competitive, so I went and picked it up there. When I buy from Ebay, though, I am careful. First I look for price and reserves, then I check feedback. And I READ their feedback, I don't just look at the numbers. Sometimes the negs they have received or given can tell you a lot. Next I check shipping amount, and if they accept Paypal. I will bid a little higher if everything is excellent, as will most people. You just have to be careful not to pay more through bidding than you would pay somewhere else!
Just a note, Amazon offers a lot of different sources for items like this, private sellers. Check their ratings too, it's no different from buying on Ebay, as far as I can tell.