The original MagicJack required you to leave your computer on all the time to make and receive calls, and didn't allow you to use your existing phone number. This was all fixed with the newer MagicJack Plus, but there are still some notable limitations. Depending upon your wants and needs, they could range from minor annoyances to deal breakers.
As with all Internet-based services, if the Internet or power goes out, you will not be able to make or receive calls. Twisted-pair copper phone lines carry power to phones, but the newer coaxial cable and fiber optic lines by which many of us are getting Internet service these days do not. There are some VoIP services that provide optional battery backups that last a few hours, but MagicJack is not among them.
Regarding E911 service, when you call 911 with MagicJack, your address can't be automatically detected. You have to register your home address with MagicJack in order for emergency services to properly locate you, and it won't work if you are using the device in other locations. Also, it will only work in cities where the Public Safety Answering Point (PSAP) has a system that can receive the address information. You will also need to make sure the address is updated if you move.
There also might be issues with getting phone numbers in some area codes. If yours isn't available, you can pick a phone number with a different area code, and switch if and when yours becomes available, although this likely comes at a monetary price.
Other more minor issues include the following:
- MagicJack is partially advertisement supported, so you will see the ads in its software. (This is why the cost to users is so low.)
- You can only control the device's volume when it is plugged into a computer. Otherwise, you have to rely on the attached phone's volume controls.
- It cannot be used to call 900, 976 or other numbers that require per-call fees (although that could also be considered a perk).
Also, if you are using your MagicJack connected to your computer, it could be felled by any number of computer issues, which might be something to consider when choosing the type of device or service you pick.