I had a positive experience with OpenSky. After reading some negative reviews, I was originally nervous to buy something from the site. However, I found a great price on a unique belt and decided to take the plunge. Fortunately, I can report that I have received my order in perfect condition.
My understanding is that OpenSky serves as a hub for other vendors, mostly small businesses and startups. I imagine that problems which others have reported were probably caused by the actual vendors and not OpenSky itself.
When I placed my order, I was informed that the item would take about five days to ship out. After five days, I had not received shipment confirmation, so I contacted OpenSky to confirm the status of my order. I received a prompt response from an OpenSky representative who promised to investigate. Soon thereafter, I received a shipment confirmation. The item was delivered on time and as described.
Overall, I am satisfied with my experience on OpenSky and would recommend it to others. I might advise, however, to research the primary vendors before making a purchase.