Thanks for the link to the reviews - I ordered some stuff when the sale notice went up a day or two ago, so now I can whet my postbeing-stalking-machete. I mean anticipation. Whet my anticipation.
The "s" in https:// in your browser bar mostly reassures you that the info being sent to your screen from the website is secure. That's one reason banking websites and such tend to use it - you wouldn't want anyone to "overhear" your account number and balance just because you checked it yourself.
Information you type into a field can get from your screen to the website owner in a number of ways, some secure and some not so much. On a site that displays without HTTPS, the "send" button can be sending to an HTTPS URL, and that's fine for the purpose but less visible to you than what's in your browser bar.
I didn't notice at the time whether he was using a shopping cart application (usually pretty safe) or a simple POST field (not really any security measures at all there, short HTTPS) - but as candre23 said, it's very unlikely that typing in a CC from your home computer would be a problem even then. If your connection is wireless, that's one reason to worry (unless the connection is encrypted). And never, ever, how many times can I say ever in one post ever buy online from a coffee shop hotspot or other public connection - because there, the chances of someone sniffing traffic trying to overhear CC info goes up by a factor of YES, ABSOLUTELY.
The best answer is to use an actual credit card from a bank with good customer service. The next best is to open a free checking account somewhere and keep no more than you intend to spend as mad money in the account, and think of that debit card as disposable - it will get scammed somehow, so make sure when it does and your account gets frozen at best or emptied at worst, you won't miss that money too badly while the whole thing gets resolved. You can also go to a lot of check-cashing places to get an "account" that you charge with cash and spend from the associated debit card, but you're far likelier to lose all your money forever that way because their customer service can be less than enthusiastic. (Sorry, I don't mean to lecture you personally; it's just hard for me to stop the safe-online-ordering spiel once it starts.)
Credentials: I haven't done web design in showing-my-age-now years, but I do IT support professionally and this is the kind of thing I often have to advise home users and SO/HO users on.