Some important points on Magic Jack.
1. They're imposing 30 minute caps on each call.
2. It's not unlimited. They won't tell you the exact limit but its somewhere between 1000 minutes to 3000 minutes. If you exceeded the limit then your service will be cut off and you need to buy credits or another MJ.
3. You can rip the SIP information out from MJ and use it on another device like ATA or Softphone. Though its not guaranteed to work everytime.
I find a good alternative to Skype in Onesuite
VoIP service. It's perfect for not so heavy users because it's only $2.95 a month with free incoming calls. Calling out is 2.5 cents per minute. Pay as you go, no plan, no termination fee.