I can tell you first-hand what the disadvantages are with Magic Jack. I'm headed back to Vonage at $25.99 per month (initial 6 months is $14.99 per month) and all the equipment is being provided free (by going back I'm getting the newest 'box').I just ordered the Magic Jack device and am hoping to get rid of my landline this week. I've read that there are definitely disadvantages to using Magic Jack as opposed to a regular landline, but there is no way our phone service is worth $50 a month. And I should be able to keep my AT&T DSL service without having the regular phone service, although it looks like they charge a little more for DSL without having the phone service bundled. The only thing about Magic Jack is everything about it is so cheesy... from their infomercials, to their website, to their "FREE TRIAL." Everything about it seems like a scam, but I've read enough positive reviews to convince me that everything is on the level. Just wish they would run their company with a little more professionalism.
To use Vonage you need internet service. The same is true for Magic Jack.
The problems I'm having with Magic Jack
1. You never know if a call is going to be understandable. Sometimes it is 'good' for both parties. Sometimes it is atrocious for me to hear the other party, but FREQUENTLY people have told me that they can not hear ME. I was using the very same phones with Vonage and did not have this problem. I had to resort to some calls using my CELL PHONE and those minutes need to be reserved for times that I do not have access to a landline, not just the landline does not WORK!
2. You can not 'port' your existing phone number (if there is a way it is not shown on their website where you can try for a 'premium' number for an added charge of $10. It still does not let you actually PORT the number you currently had in use with the other service.)
3. A friend made the mistake of turning off their laptop where the device was attached/installed, without first closing the MJ application. She had the really bad luck of having to re-install the operating system. Be really careful with this aspect.
4. I was told to make sure the computer that the device was attached to did not have a lot of applications that were also running. Well, I have a spare computer that is REALLY little used that I put the device on. It has enough speed and without any other load on that system, the service should have more than sufficient resources.
It did NOT work well enough to keep the service.