Ask HN: Payment systems that don't suck?

It has been a long while since I've played in the arena requiring interactions with payment systems. There is a lot of buzz around iTunes for in-app payments, FB credits get mentioned as well. However, for your general web app, have things gotten more graceful than the good ol' days of multiple paypal screens / etc?

What are the credit card transaction systems that provide for the most seamless site interactions?