I should note, however, that there is one circumstance where I would possibly accept DCC. If I were stuck with nothing but my Canadian credit/debit card I would take it over the double-whammy TD slaps on foreign transactions not in USD/EUR/GBP/AUD- for transactions in other currencies, say in JPY, TD first converts to USD +2.5% then to CAD +2.5%, effectively taking a little over 5% as a FX commission. Direct conversion to CAD only happens with those four currencies.

This was fairly well-hidden in the cardholder agreement and I only noticed when looking to make sure that the 2.5% listed currency conversion fee was just for forex and not for all foreign transactions. Of course, actual Canadians have more choices than I do, and thus would be able to avoid this problem with a 0% card from Chase. Sadly, the DCC-proof AmEx would be even worse for Canadians because AmEx Canada converts all non-USD foreign currencies to USD before converting to CAD, making it not worth it unless buying something where purchase protection was necessary.