When one field is valid that field no longer appears editable, so if there was a mistake in the spelling of my name it took me a minute to figure out I can still click on my name to change it.
It doesn't tell me the card number is invalid until after I enter an expiry date, that may be legitimate but it caught me off guard.
I don't like it. It's too confusing for what should be name, card number, expiry and security number. It doesn't address the fact that after I fill out those four fields, I still need to enter my billing address in what would be at least four additional fields regardless.
One great optimization skeuocard has is it only asks for the cc# at first, then the other fields appear as you type it in. So the form is less daunting at first.