Looks very nice, I like being able to design your hosted payment page. Does the "thank you page" redirect pass along enough information to be able to associate the subscription with a user account? Also, do you plan to do some kind of URL postback for when a subscription's status changes?

I was a little bummed to see that your ToS doesn't allow adult, but I also have a dating site client who will be needing subscription billing soon. :)

Edit: Ah, yeah the net 60 is kind of rough.