I just setup and tested the new shopping cart for credit card payments. I really like how it looks and how simple it is.
However, there is one small change that I think would help.
I did a test transaction and I got an error. I went back and realized that I didn't change the credit card expiration date. Since this is auto filled out, it allows the buyer to continue without entering anything. If someone is in a hurry they may not notice this because all of the blanks are filled in. After getting an error they could turn away. For my case, the default month was correct but the year was off so it didn't seem to stand right out.
For the expiration date, I suggest that it is blank and nothing is auto selected on the dropdown by default. This would force the user to make a selection before the transaction can be processed.