The Global Shipping Program has its issues, but the biggest one seems to be one of sellers using it inappropriately, either because they haven't done their homework or else they've found themselves "mysteriously" opted into it.
For some items--particularly larger or high-ticket ones--it's actually quite a viable option for international shipping. It's certainly preferable to shipping the item by UPS or FedEx Ground where taxes and customs fees are due on delivery, and those fees are usually a lot more than what the GSP wants.
The hiccups to all this seem to be fourfold: Sellers can't offer combined shipping on GSP listings, getting all your money back in the event of a return is a laborious process, there's no transparency when it comes to being billed for the taxes and fees involved, and items sometimes get repackaged by the Global Shipping Centre quite badly.
