The problem with international shipping is import tax. Not that we can't buy with bitcoins.
Import tax will be there even if you pay using credit card.
But you will save some money on foreign transaction fee using bitcoin.
I also expect overstock to give some discount for those using bitcoins, after some time.
After all, they make some savings on the credit card transaction charges.
I would not at all be surprised if they are the first major merchant to do this. Once they would implement some kind of discount for paying in BTC they will likely set a precedent for other merchants. (I have read about newegg having some kind of promotion for people that buy a specific product in BTC, but I think this is too specific to be considered a "discount" for paying in BTC).