As a buyer I had mainly good experiences, but I always check with the seller if it is available and check the pictures, then I pay with Paypal and fund it through a credit card, in case there is a dispute, I can dispute the payment and have some security, happened only once and they took the item back as it was a different item than pictured.
As a seller, horrible, they lost one item in house for ages, I could see it arriving there and going into quality check, passed quality check and ready to send, then nothing for 8 weeks, the buyer lost patience and canceled the sale (I know because she left a message under the item, where I gave her the tracking and told her it has been received, went through QC and I don't know why it has not been sent) after 2 months (!) and the buyer telling me they are canceling it now, they contacted me and claimed the measurements were half a centimeter off, they wanted me to sell it for a massively reduced price, I declined, that was all in October, now this week (mid January) I get my item back. Well, strangely enough with their tag that it is as described, it is authentic and in very good condition... I attach the picture of the label, my item which I got back from them...