Upvoting because this is so beautifully executed and I'd love to see people test this out on their checkout process. That said, my experience indicates that this is not going to convert well. To mirror the author's own quote: "Every question a user has to ask themselves during the checkout process is another reason for them not to complete it." What's presented here is a drastically different experience from the norm…
Thank you for being willing to test it! This isn't something I'm making money off of, nor is it something I feel the need to ram down people's throats -- I just wanted to try something people hadn't seen before. If it works, and people like it, great! I'm glad to have helped a little. Please let me know if you run into any trouble (my Twitter and email are on the site).
Unfortunately, for unrecognised card types it makes it impossible to proceed. I have just tried a maestro card number (beginning 6759) and am unable to enter any of the additional details (expiry, etc).
It may be worth adding a generic fallback for cards that are not recognised to account for unexpected edge cases.
Keep up the good work!