Google is now offering a credit card for AdWords billing. Its a MasterCard credit card that can only be used for your PPC account, not for any other purchases as stated by Google: The AdWords Business Credit card can only be used with your AdWords account. If you try to use it for purchases outside of AdWords, the card will be declined.
On the AdWords credit card signup page, the main benefit is to keep your click charges separate from your other business expenses for neater accounting. I’m not sure how this would be any different from having some other type of credit card used solely for your AdWords’ charges.
I do think that its a good thing for Google to provide other financing options. Many accountants get annoyed at the $500 billing thresholds which Google enforces. Other alternatives to that predicament would be pre-paying for clicks, or applying for invoicing directly with Google.