Depending on when you go, they *might* have a hack software unlock solution, but I wouldn't bet on it right now. For unlocked iPhones, the best bet is always to buy them in a country where they sell unlocked ones - which is what I do. I offer them for rent for travelers that want to use an iPhone where they go - since Apple hasn't released the iPhone4 internationally yet (July 30th is the date), I don't have any yet (I do have iPhone 3GS', though).
I'd stick with them, they don't have the design flaw.