Not sure about your specific question re the World Phone, but I have usedf a 4 band GSM Motorola phone with Cingular/ATT contract, international roaming, and it works just about verywhere in the world.

There are many threads around here dealing with international cell phones and the best way to go. There is no one right answer for everybody.

For me, I wanted one number that my kids/family/friends could dial a US domestic number and reach me wherever I happen to be. It is for emergency contacts, not chit-chat. The quad band GSM with ATT/Cingular service meets that need.