Nahhhhh. It's actually worse than that. Now you have "another fucking processor to have to" TEST.
Adding paypal to a checkout process will often result in a loss. Give people too many options late in the game, and you'll fuck up your sale. (Present them sooner as well... but same diff when it comes to asking people to get their card out. Your stated payment options often aren't all that relevant until a person is asked to pay.)
I suspect the paypal (webmaster) crowd will differ from the amazon (consumer) crowd, but it's still an issue that requires testing. More options are not always better. Everyone says more options are better everywhere, but time and time again, I have tons of data to prove more payment options does not equal more profit. It often creates more abandoned carts. You have the sale... the customer is listening to you... and then you let them go and make their own decisions regarding their payment preference. Their credit card is in their pocket, but their paypal password is at home.