Funny how omitting a few details makes it seem like it deserves the title. While most of what it says is true, it fails to talk much about the "import restrictions" that it briefly mentions:
"Amazon does not have an Argentinian site and import restrictions make it a bureaucratic nightmare to purchase books from international internet sellers"
This problem is not only one for international sellers, but for international publishers. As a publisher these days it is almost impossible to get into Argentina. As an Argentinian bookstore it is prohibitively expensive to bring books from foreign publishers. That's a huge problem and very far from what the linked text paints.
TL;DR: +1 on making the "Remember me" checkbox optional.
I'll try to offer a slight variation on what others have already mentioned regarding checkout. Like many of them I find Stripe to be very well thought out and easy to implement.
As far as Checkout goes, the idea is great but it might need some updates in order to make it more useful to a wider audience.
As other mentioned, the "Remember me" function was enough for me to not use Checkout. It is confusing, perhaps because it introduces a mental shift in the user's mind, where out of a sudden they need to understand how this other company "Stripe" will magically keep their info across devices. A way to hide that field wouldn't harm anyone (other than Stripe's ability to do branding).
It would also be nice to allow style customization of the form.