For its intended use, this add-on does exactly what I want - when I type in Amazon's URL, it redirects me to the smile website. This is something Amazon's official extension does not do.
Unfortunately, it does have a rather annoying bug - If I click an Amazon link and am not logged in (e.g. Amazon US or Germany product link, but I'm only logged in on the UK website), it gets stuck in an endless loop trying to redirect to the smile URL. It would be great if it detected the redirection attempts and temporarily disable itself to let me access the page, maybe with a warning bar stating that I need to log in and click retry.
I also wish there was a toolbar icon that let's me temporarily disable it, especially in private browsing mode. For example, if I'm browsing Amazon for gift ideas, I certainly do not want to log in!