Hosting platform isn't too bad, but changing payment API is a real pain since it's basically impossible to move existing subscriptions to a new system without user interaction.

However, I think Chargify is probably the best route for anyone doing subscription based stuff. Managing billing for subscriptions is such a pain in the ass, and these guys seem to understand that at the core.

I'm on Amazon SimplePay right now and I'd switch to Chargify in a heartbeat...if I could move over my existing subscribers ;)