We've started using our AMEX exclusively. We were using an AA Citibank Mastercard until they started charging us 3% on every purchase even if it was in USD.
They had not been charging us (saw that many people were charged) as they said we were, for some reason, exempt. When they started charging and we checked Visa, AMEX through Bank of America, Chase, etc. we switched. There are a few places that won't accept AMEX cut not many - for those we just use our debit card from our Aruba bank.