I sometimes transfer money between my American and Australian bank accounts using Forex, which of course means paying a service charge. Would I be able to get a better exchange rate if I, say, transferred Australian $ to bitcoins to American $? I haven't bothered to look into it, but I guess it's possible that that would be cheaper. Wouldn't have to pay any $ to Forex, but I'm assuming that bitcoin has its own user fees?
Given the volatility and potential for theft you are exposing yourself to by using bitcoin I don't know what the savings really are. FX fees and spreads can be brutal. This business of credit cards in the US now charging fees on top of spreads for foreign transactions even when the transactions are dollar denominated is absurd. I was hopeful a different system would come into being but given what happened at Mt. Gox I am justifiably concerned.