Most well run credit card companies have a protection policy just in case something like that did happen, and if this guy is based in the US then you would more than likely be covered. I believe that a few hold you liable for the first $50 but you'll have to check with your card holder for more information.

Also, many, but not all credit card processing systems/companies don't even let the retailer view the full credit card number, just the last 4 digits and the card companies name. I checked out the site but their processor seems to be transparent. Some online store fronts do this, especially when they are a small time operation, in order to look bigger and consequently more professional. However, I could see this being used negatively as to make it harder to for you to perform a chargeback.

I honestly doubt you have a much to worry about other than the remote possibility of him not sending you anything. I've never used them so I can't comment on their service but from what am able to gather they don't seem to bad.