Anyone have any experience with a company called Mobal?

http://www.mobalrental.com/

Looks like if you have a GSM phone which works in Europe, you can buy a SIM card for $19 and then pay just for the calls you make/receive. While the rates aren't nearly as good as pre-paid cards purchased in other countries, it seems like a good alternative for somebody who doesn't expect to make a lot of calls but wants the option available and for people who might be in multiple foreign countries and not want to have to buy prepaid cards in each place.

Any thoughts on this?

cnk