There are some bad shipping options out there, and I'd wager most small business owners have shipping horror stories, but Global Express Guaranteed is really a special kind of hell and I think folks deserve a fair warning.
GXG is a joint offering of the US Postal Service and FedEx. The idea is that you pay the USPS for postage and insurance and ship your international package just like you would with regular mail, but at some point the USPS hands it off to FedEx for final delivery.
It's the unholy union of a government entity and a private shipper in a poorly-structured and executed agreement that makes it such a uniquely awful experience. On the surface it looks fairly attractive - the rates are lower than you'd get from FedEx, and it's not quite as fast but the quoted delivery times are still competitive and it's supposed to be a time-definite delivery service.
I've used it several times over the last few years, and more often than not it's gone poorly. For starters, the guaranteed delivery has a whole bunch of catches - you can't even find out what the guaranteed delivery date will be without visiting a post office in person, and only certain post offices will accept GXG packages with a delivery date guarantee. In my town, that's inexplicably the small satellite post office on the edge of town and not the main post office.
It's when there's a problem with the shipment that things really go wrong. If you call the post office, most of the support people there haven't even heard of GXG and don't know how to handle it. Same for FedEx - I had one person there hang up on me because they insisted it had nothing to do with FedEx.
My most recent (and final!) experience with GXG has been infuriating. We had a > $2000 order to ship to a big theatrical company doing a special show in Saudi Arabia. These were custom-made props. The shipment went out on August 8, fully insured, with a delivery guarantee of August 17. The total for shipping and insurance was over $960.
The package disappeared from tracking after just 5 hours of movement. A missing mail search turned up nothing. We had to drop everything and build a replacement order that cost $1400 to ship by DHL. That one made it through just in time. DHL has their problems, but they've always gotten packages where they need to go for us, or have paid up on insurance claims when they haven't.
Meanwhile, I was instructed by the USPS to file a claim with FedEx. I followed the instructions to the letter, and have screenshots to show it. FedEx denied the claim because they had never received the package. USPS insisted that it was still FedEx's problem. FedEx wouldn't even talk to me. Eventually USPS said the issue would be escalated to the global business office in DC and that they'd be in touch soon. It's been weeks, and the support ticket has been closed - there's no further escalation path available there.
But this week it got worse. The original package reappeared and was handed over to FedEx and now it's stuck in customs in Saudi Arabia because there's no one there to receive it and pay duties. FedEx refuses to do anything about it because as far as they're concerned it was shipped last Thursday - the day the USPS finally found it and handed it over. They want return postage or it'll be destroyed. At this point the package isn't worth the $900 it'd take to send it back - the items were built to order and at this point would have to be refurbished anyway after so long packed up.
Because FedEx didn't take the money for shipping, they can't even be sued in small claims court. Everyone involved can just stop responding and there's no way to force a resolution short of federal court.
Neither the USPS nor FedEx are bad shippers. Both have their resolution processes and at least a certain amount of accountability. But the GXG program is run so poorly that there's basically no way to resolve issues like this. Avoid the service at all costs.