I'm not sure why you're posting this to the eBay Canada discussion boards as American sellers don't generally hang out here. You'd probably be better off posting this to the eBay.com discussion boards, but let me give you a bit more information before you head off to the lions' den.
Those "import charges" you see on GSP shipments don't generally have much if any duty factored into their calculation. What you're usually getting is an estimate for HST or GST plus clearance fees of around US$4-5 dollars. Anything sent by courier or its equivalent is subject to PST/GST/HST charges if the declared value of the shipment is above C$40.
For what it's worth, most of our American cousins now have to pay state and local sales taxes on their eBay purchases no matter where they're from and no matter what the value is. Because of this, you may not get a lot of sympathy on the American discussion boards.
As for the shipping time, keep in mind that what you're getting with the GSP is a glorified forwarding service. If the seller chooses a slow shipping method to get the item to the Global Shipping Center in Kentucky where GSP-forwarded items are processed and forwarded on to their destinations, that's going to affect the overall shipping time for the item as much as anything Pitney Bowes (adminstrators of the Global Shipping Program) does or doesn't do. I'm on Vancouver Island and I've used the GSP mostly to buy mobile phones because the GSP shipping and clearance charges are dirt cheap compared to most of the services offered by couriers. I've purchased cases for my phones at the same time as I've purchased the phones themselves. The cases weren't handled by the GSP but in all but one instance the phone arrived before the case. As you live in the Centre of the Universe, your experience is obviously different.
No question the GSP isn't a good fit for most US-to-Canada sales because we live right next door to the US, we enjoy a pretty good trade relationship, and our mail services are generally competent. However, the GSP serves about 100 other countries in addition to Canada and most US sellers don't have the volume of sales to Canada to justify making an exception for us and doing the extra work involved for a more direct shipment.
