Very true, please count me as one of your satisfied customers. In a different comment, I did say Spreedly would be a great fit for those who just want a straight forward recurring billing solution, without deep API integration and other features offered by Chargify/Recurly. I forgot to note that here.
Deep API integration translates in to 'more lock-in'. Better try to handle as much of the business logic other than the initial add, the rebilling and the deletions upon account expiry yourself.
Keep your interface to services like this as thin as you can get away with without compromising customer comfort, in the long run you'll be very happy you did.
