There are better solutions, and for a fee you can get everything (and more) that the phone company offers in a VOIP solution. Problem is for each new feature and dependability the costs start creeping up, and everything is based upon your internet connection.

Magic Jack is on the low end of the cost scale, and being the low bidder it has the most limitations. I agree with Zarf4 that the Obi is a strong contender. I have one that I use for my fax line, as I found it to be insane to spend $30 a month for the infrequent faxes that I send and receive, as I could buy the box for just a little more than one month's old phone bill. I've been using it for about a year and have been very happy with it. It interfaces with your Google Voice, but also allows you to use a SIP service, so if Google Voice goes away, starts charging too much, or whatever you have another option. Also you can port your existing number to a SIP server that will then be your new phone company. I haven't done this so can't vouch for any company, but there are quite a few and they offer as much or as little service as you want, some even offer 911 and a block of long distance, domestic and international minutes each month. Again you can buy whatever you want, and it is cheaper than your local phone company.

Another option would be to get a cordless home phone that has bluetooth. This will allow you to use your cellphone as your home phone. I've seen some inexpensive multi handsets that allow you to do this. You could also use an Obi, with the bluetooth cordless phones. This would give you 24 hour access to your Google Voice number, and a home phone when you aren't there with your bluetooth cellphone. With your cellphone attached you could also have 911, provided your cell provider offers it, and if your internet is down you still have a working phone.

Another thing to remember is to put all of this on battery backup so when the power goes out you still have a phone. I have my cable modem, router and Obi box all on a UPC. Of the three the wireless router draws the most power, especially when it is in use. I wouldn't even consider switching over to VOIP unless you get a UPC for all the devices. A consumer grade box is fine, just make sure it has enough juice to power the equipment, for at least an hour - for a long outage you can power it up when needed, but when it's off you can't make any calls.

You are saving at least $30 a month, but you are going to have to buy some hardware and maybe a small monthly service fee, so be smart and use a little of the money you are saving to make a system that is dependable. With a little research it really is simple to give your local phone provider the boot and get more features at a much lower cost. If your internet isn't dependable, and relatively fast, then you need to remedy that issue before you switch to VOIP.

For a second line it is a no-brainer, as you will find out very quickly if there are issues, and still have a landline. But like computers in general you need a backup if it is your primary phone.