I use it for small recurring payments to some online services. Some online services only accept Paypal so I just pay via Paypal using my stored Amex/Visa detail

I use it for small recurring payments to some online services. Some online services only accept Paypal so I just pay via Paypal using my stored Amex/Visa details and Paypal process the payment and passes it on to the service operator. Does exactly what it says on the tin. Also means I only need to update my card details in one place when I switch cards or get a replacement card. No problems and in some ways the UX is better than using a traditional Visa/MC/Amex processor.