The one time I bought a piece of camera equipment on Ebay, it worked out. It was a new in box Canon telephoto lens for about half the retail price. I sold it last year and got almost what I paid for it.
Seems like I'm one of few here who likes Ebay, but I'm not one of those e-seller/store types either. I'll sell or buy something once and awhile. I have 200 Ebay transactions and have only been ripped off once.. A seller from Canada (50 bucks). Stay away from overseas purchases (or Canada.. Canadians will rip you off. Sorry, but true). Check the seller's feedback rating before you buy and the number of transactions they've had is important too..
Ebay is great to use if you have an item and want to see what it's selling for.. Find your item, bookmark it then return after auction close to see what it sold for. Hopefully, it wasn't the seller who falsely "shill bid" the item up.