A Review: Cheap Phone Calls to any part of US and Canada!

I'm one of the users of this device, it is called MagicJack. I was amazed by this device because you can call in any part of US and Canada for just $20 a year!.
I'm currently at Philippines and I can call my Parents at the U.S. without any hassle of buying International Phone Call Cards or any Domestic Phone Lines.
You can use this device in any part of the world unless you can only be allowed to call US and Canada. I'm not sure if you can call in other countries, maybe there is a huge charge is there is.
MagicJack is a device that has a USB to plug in your computer and has a phone jack that plugs in a standard phone.
It is a computer peripheral that, in combination with telephony service from the related YMAX Corporation, provides Internet Based Telephone-Service (VoIP) to the United States and Canada. The firm's primary product is a  USB device that holds both the software necessary to place Internet-based telephone calls via a customer-supplied high-speed internet connection, and electronics (technically known as a SLIC, or Subscriber Line Interface) supporting conventional landline telephones to be plugged directly into same device. The products are promoted through television infomercials and a website.