I don’t have any personal experience as such with using their services, but I did review their product before travelling abroad. The prices quoted by them for making a call to India when u are abroad are exhorbitant. For example, before going to New Zealand, when I contacted them I was given the outgoing call charges as 4NZ$ (approx) for a minute to India and 1.4$ local. Of course incomming is free. I knew it was very costly because there were a lot of other options available on the web, much cheaper both on outgoing and incoming calls from NZ. When I told their executive that their rates are very high, he tried to his best to persuade me to take it. But I did not.
Actually I would like to advice all people, take a local pre-paid sim card. There are various options which works out much cheaper. And buying a local sim is very simple, easier then buying the same in India. (I have bought local cards in Singapore, Maaysia, UK, Australia, New Zealand) There are various offers and service providers. In fact the simcard which I took in NZ offered me calls to india at an unbelievable rate of 8 cents per minute!!! (around 3rs per minute) local calls were costlier at 44 cents, but still cheaper than what Matrox offered.
So DONT BUY MATRIX, TAKE A LOCAL PRE-PAID SIM. ITS VERY EASY.