I started to shop for a drivetrain upgrade and many Shimano parts are currently out of stock almost everywhere. Ebay has some groupsets with good pricing but I am skeptical if they are real factory parts or seconds. Many ship from China or Hong Kong. Beside even if Ebay says item location in in the US they often ship from overseas. It is even questionable if they come in original packaging.

So I am looking for experiences with Ebay stuff. Good and bad.