Also have a fierce loyalty to AmEx as a customer. I use it as often as I can to pay for things. Their customer services is phenomenal, and its nice to have an arbiter between you and a merchant when things come up. Anytime I've had an issue with a merchant, I try to work with them first, and then jump to Amex if they aren't willing to work with me. In every instance Amex has been able to fix the problem, typically by refusing payment to the vendor after an investigation. It's like having insurance for your purchases.

I say this as a generic green card member of 25 years. I know a lot of people pay for higher tiers for travel benefits, but the base service has been excellent for my needs.