My flight has landed and my iMac is now on its way to its destination sort facility. Based on the last Apple item that was shipped directly from China (my iPad 2), when the item is at this step in the shipment process, it should be delivered the following day. In other words, I should be getting my iMac tomorrow. I don't expect any more tracking updates tonight but things should get going again tomorrow morning.
Nothing sweeter than "out for delivery"