To me, the most important drawback is the inability to defer charging. It honestly breaks my heart to want to tell someone "thank you for that, have a free month of service" and then to see that you can't do that because they already liked your service enough to support you.
I see a commenter mentioning PayPal reference transactions, I will give those a go and see if they are more flexible.
I agree, free subscription time is my favorite thing to give. I can sort of do it with Chargify. It basically works as a partial credit toward their next charge. It's not exactly the same as deferring a payment, but it pretty much works out the same.
I see a commenter mentioning PayPal reference transactions, I will give those a go and see if they are more flexible.