In Canada we're using CheddarGetter and paypal to accept USD, however as an Australian (Living in Canada....) i know exactly what you mean and have been through it before.
I seriously suggest you look at Paypal, if you want to make switching easy however, abstract the implementation as much as you can. We're using CheddarGetter to do the abstraction for us, its $79 / month for CheddarGetter...but any half decent programmer who i trust with our billing doesnt cost far from that per hour anyway. Its a cheap means of getting around some smelly situations!
I seriously suggest you look at Paypal, if you want to make switching easy however, abstract the implementation as much as you can. We're using CheddarGetter to do the abstraction for us, its $79 / month for CheddarGetter...but any half decent programmer who i trust with our billing doesnt cost far from that per hour anyway. Its a cheap means of getting around some smelly situations!