Late in 2010, WorldPay gave me 60 days notice that they would be pulling out of the Canadian market and that I'd have to look elsewhere for credit card processing. The way they handled this could easily be covered in a series of blog posts. Let me just say that, after years of great service from WorldPay things have ended on a very unsatisfactory note for me. I won't be encouraging any more of my clients to go with WorldPay as a billing solution. There are better solutions out there and there are companies out there who will treat you with more respect. That's all I'll say about that for now.
The good news for you is that, as of now, single credit card payments are handled by PayPal. So, if you're already a PayPal user, you can now make WunderCounter payments either by creating a subscription (recurring payments) or you can make your payments manually when they come due. This gives you lots of flexibility. It gives you the hands-off autobill approach or the hands-on manual approach. It really comes down to what you prefer and it makes no difference to me which path you choose. :)
If you don't have a PayPal account, you won't be required to create one in order to make a single (manual) payment, so it won't be much different than making a payment to any other gateway. The difference is that PayPal will handle your credit card details (rather than the WunderCounter) and that's a good thing.