In 14 trips I have never had a merchant charge me extra for using a credit card - at times I have offered to let them add it and still have never had it added.

Took travellers checks my first trip, would never do it again as it was way too much hassle. The exception to that would be having them cashed by the hotel, which was easy enough when they had the available cash.

I can never remember which is better . . . safe? . . . or sorry?