Just to reassure you, I've used Magic Jack for three years...actually, a little over.
It has never given me the first problem.
I call a friend in California (all the way across country) once in a while and talk to her for hours.
The call quality is great and no long distance charge!
If you have no trouble with your broadband connection, you shouldn't have any trouble with Magic Jack.
"Best not to think about it. I don't want to fall to bits 'cos of excess existential thought."