It really depends on where you live and your internet company. I use Vonage, and I have never had a problem with it. The sound is the same quality as a normal land line, and it never disconnects calls or anything like that--it's the same as a normal phone. However, we live in a very urban area (JUST outside of DC), so we have a very strong cable internet connection. If you live somewhere where you have a weak signal or you have frequent internet outages, it's probably not a good idea. I have a coworker who lives further away from the city and said their Vonage sucked--always sounded like static and unclear, but I have never had this problem.
You may also want to check with your cable/internet provider--a lot of companies are now offering cable phone service (around here, anyway--don't know how widespread it is yet).
Highest known weight: 324
Weight on morning of DS surgery: 308.5
Got down to about 185 before pregnancy;
Benjamin David born March 24, 2012, 7 pounds 11 ounces