Vonage's Cheap International Calls for iPhone

Vonage has just released a new application for your iPhone which allows you to make cheap international calls over 3G or Wi-Fi from your device. Currently early adopters are getting 15 minutes for free if they choose to download the free application, but even if you had to pay for the service, it's still quite cheap. Just to give you an idea, you can call anybody in a list of 100 countries for 15