Amex is badass. They are the only financial institution that I don't regret having to call. Plus they allow a lot of things that other banks haven't yet implemented like unlimited online payments (BofA only allows 3 a month, Citi only 4) and the ability to activate and do other functions that usually require a lengthy phone call with other banks. I'm all for em to compete with Paypal. However, I doubt that they will make a sizeable dent.
Edit: However, I hear merchant side Amex is pretty terrible. They charge a lot more than Visa/Mastercard per transaction and a lot of joints in my area don't even accept Amex.