I've bought a bunch and never had a problem, like people said above, buyer beware. Check feedback and what they have sold before. If they have sold other optics and hunting stuff you are probably ok. If you use PayPal you do have refund protection through eBay if you do get taken.
x2. I've bought and sold hundreds of items on Ebay and never one problem, knock on wood. There are so many fraud and buyer protections now with Ebay, Paypal and your credit card that it is near impossible to get screwed.