mate i'm in aus too and i had a friend in the states and i was worried about the exact same thing.
and i was ******** myself just before i ran ziphone, but i can honestly say that it was soooo easy and its now working perfectly.
you should get your mate to send back a few and sell them to make back some money - i got 2, unlocked the extra one and sold it for a profit and i also sold my ipod touch so it meant that i made a transition from my ipod to the iphone for no extra cost
have a crack mate, its too easy