One thing to be aware of is that while many of these products are "Fee Free", the exchange rate used in the currency conversion may have a "hidden" inbuilt arbitrage that can be significant.
they dont and cant have hidden inbuilt arbitrage.
since late 90s (quick guess) Aussie banks are required to highlight any 'profiteering' by charging as seperate line items on the credit card statement, hence the '3% overseas transaction fee" was born. A win win for consumers so was said, but formerly when the banks did add a margin hidden in the conversion it was definitely less than 3%. I forgot exactly how much though, but as a bank jerk in the 90's i did the math myself on my own transactions and would always tell the customers to just use debit/credit card rather than TC's or cash as the conversion was so much cheaper.
The Visa/MC card schemes in australia transact with the banks in AUD if you find they have added something for profit, then lodge a complaint as that would be a serious breach of their own T&C as well as banking codes of practice.
*note: Citi and HSBC do some funny business with their foreign currency accounts when linked to debit cards. avoid these.