I just signed up and made a call to the PI, no problem. You can sign up online and activate right away. 8.9cents/min to landlines and 10.9-11.9 cents/min to cell phones. rounds to the minute (not 3 min). No connect fees, weekly fees, etc. NO fees, no minimum usage, no nothing. You can even register your phone number so you don't have to input the PIN. Pretty straightforward!
This is much cheaper than skype and was by far the cheapest calling card I could find with no minimum usage, rounding up to 3 minutes, etc.