In Ecuador they use US bills, but for coins they use a mix of US and their own. When you get change from someone, you'll geta random mix:

As far as I can tell, no one has a preference for the US versions of the coins. Even though the US ones would be useful all over the world. This is kind of strange: you would expect to see people holding onto the US ones and passing on the Ecuadorian ones. Does this just mean that people have enough trust in the government's plan not to overmint that it's not worth the hassle to deal with sorting?

All fake bills will be will be perforated

(This also suggests a use for the billion extra dollar coins: send them here.)

Update 2012-05-19: apparently they listened to me! Ecuador is importing ~12% ($167M of $1.4B) of the excess dollar coins.