Just a Phone Call Away to Saving $300 A Year???

Heard about this phone service called Magic Jack - I have personally talked with someone who has it and really loves it.  Have you heard of it before? We are currently spending about $30 a month for our land line, or about $360 a year.  Supposedly with Magic Jack we can cut $320 dollars off that price the first year and $300 off every year after that.  They charge right at $40 the first year and $20 every year after that.  That sounds amazing to me!  We tried going to cell phones only for a while - we did not have reliable enough service to continue but I sure would be willing to try this thing out - it can't hurt and we might end up saving a bundle!  Feedback from you guys always welcome.