I think Cheddargetter is friendly to bootstrappers - they have a free plan for up to 20 customers.
Recently been thinking of changing to Chargify now that they support a payment gateway in Scandinavia. We (http://beaconpush.com, push service for Web Sockets) currently have our custom-built system for recurring payments. It works, but I really don't want to spend time hacking on it. I rather be focusing on our core business of developing our service.
"Unfortunately your transaction volume was too low to be approved for a merchant account at this time. "