I have 3 Magic Jacks.
So for $50 for the device (includes first year of calling) + $10/year for stupid CTRC rules on having a number + $140 for a 5 year calling deal, the 6 year cost is $250/6 years = $42/year = $3.50/month.
That is for call display, voice mail (+ voice mails sent to email) and unlimited calling in North American.
Compare that to my land line at $80/month, and my payback was about 3 months, made the decision a no-brainer.
Magic Jack even has great customer service.
I'd never go back to a land line or even a VOIP directly provided by an ISP (as they charge about $15/month for basic calling).
I do have a cell phone as well, so 911 is handled by that or the fact that for Magic Jack, you enter your street address into your profile.
One added bonus, so many fewer unsolicited calls as your number is now unlisted (which I used to pay for!).