We have Vonage, And it works great the only time it used bandwidth is if your makeing or receiving a call. On top of that my wife is on the phone all the time and the bandwidth it does take up is not that much. It sounds just as good if not better then regular Phone line. And has a few added features that sold us on it. We move alot i am in the military so all we have to do is unplug the router take it over to the new house hook it up and that is it as long as you have highspeed internet you have a working phone. We even took it with us one time to a hotel, the hotel had highspeed internet hooked the router up pluged the phone in it and we had our own phone.
On vonage you can do the same things you can on a regular phone but it has a few things that i never seen on regular phone. For voicemail we log on to our account and we can play the msg right threw the computer. I dont even have to pick the phone up to dial i use my computer.
The only problem i have seen with it is that you can only run 5 phones off of the router i know that is alot but we have one in each bedroom front room and then a fax machine.
All in all i say get it MUCH cheaper and not one time has it went out on me when i pick up the phone it works.
Lotec