The Checkout page should have two options - "Credit Card" and "PayPal." The processor for the "Credit Card" option is also actually PayPal, but it is the seamless version where the customer does not actually leave the website to process the credit card transaction. The PayPal option takes the user to a PayPal check out page to complete the transaction and then return to the site. (Note, as of writing this the Credit Card option has been hidden, since it does not work properly.)
Currently, neither option is working securely (under https://) and when the Customer clicks to proceed from the Checkout Page, the user gets a warning that they are sending an unsecured form. This will likely give them pause to complete the transaction, abandoning their shopping cart and loosing them as a customer in the future.
Even if a registered/repeat customer logs in to their account on the site, once they leave the shopping cart page, which IS secure (shows appropriate icons in the browsers), the Checkout page is "unsecure".