I'm also curious about this as well. i'd much rather download this game.
EDIT: Hmm, it should be noted though, that this credit can only be used for the purchase of video games sold by Amazon, unlike the $10 credit from the other platforms, which allows you to apply the credit to aything sold by Amazon.
Thanks for pointing that out Hoyte. At this point, I've no doubts this is real. So despite the fact the credit is a bit more restrictive on the download, I'm going with that instead of a boxed copy.
Just a word of advice for other downloaders: don't download directly from Amazon. A lot of people were complaining about the Amalur download not playing nicely with Origin. Just take the code Amazon gives you, plug it into Origin, and download directly from Origin. Despite the other complaints about Origin, I'm able to max out my 15 Mbps connection when I download from it.
Strange, the download is just an ISO, maybe I was the only one that didn't have this or the other pre-download problems that everyone has been having with this game. It installed just fine on my machine, and I also bought Syndacte which is Origin based and a number of Steam based games, and they installed just fine as well. I also got the code for the rifle dlc and the 10$ rebate that I used on Wargame: EE and that went through as well. I use IE9 for amazon, because firefox does not get the amazon website right for some reason (I think it's either Java or Flash on firefox). I don't know if it's the web browser or the special software I use (DEAMON Tools Lite) that make the ISOs I have install right. I also disable Antivirus when installing from amazon.