Haven't tried it, but if you go through and sign up it appears to be $10 / month for VOIP service and then you pay $5 more for CDN long distance on top of that. The going rate for unlimited VOIP is $10-15 / month, so its not that cheap. Of course if you can convince a couple of friends to join then its it'd be a pretty sweet deal for you at least
.
I currently use acanac and am happy with their service:
http://www.acanac.ca/
I bought my own adapter ($50 from canada computers) and then I just pay $120+tax for a year of service with unlimited US/CDN long distance. Been with them 2 years now with no issues.