Hannah of coral cove sold on ebay for a good while, and I know she has quality stuff. Like anything else on ebay, or for that matter anything online, the experience you have has everything to do with who you buy from.
Im sure there are some good experiences and good sellers. Im just finding out personally that a lot of the stuff I purchase online does not survive all the stress of shipping and acclimating. Then again i have not bought coral online yet. Im just speaking from experiences with fish and inverts. Some deals just are hard to pass up and are worth the risk. Either way I still would not buy bristle worms off ebay. Lol