Mine were sent registered mail via China Post. I have had an 80% success ratio, 2 out of 10 just never arrived and I found out later they had been sent back for non delivery.
The biggest issue is when it get's here. I tracked the items on the Post Office international tracking page using the international tracking number received from ebay. Once it arrives at SAPO the number is supposed to change to a local tracking number. This never happened. In the past I have phoned the SAPO call centre, and they have given me the local tracking number and Post Office it is being sent to. This last time the call centre never ever answered and the customer service email remains unanswered. Eventually I received an SMS from the local post office to say it was about to be sent back. I never received any notification from the Post Office, nor sms's before this. They claim they sent notification to our postbox but that never arrived. I have kept my purchases to really low value items, just in case. I have bough Fishman pickups, guitar case hinges and clips, machine heads, Bridge saddles etc on ebay. I would not buy something expensive. Use a Courier service, even though the cost is huge.