I've used the Global Shipping Program on a number of coin sets I've sold over the past year to international buyers. Very easy on the seller's end; you just pack up the goods just like shipping within the US. At least for me, they go to some place in Kentucky, where I assume they get either repackaged for international shipping from there.
One thing is strange though. If someone wins multiple auctions, you can't send them an invoice for all of them (and knocking down the shipping costs). I've had more than one buyer question this, and I thought was weird too, until another buyer told me that they pay all the shipping up front, and then ebay refunds them the difference once the items ship.