interesting, i was just talking to a phone guy and he's exact words are "Vonage is the best of the worst". he thinks VOIP is decent for residential service but terrible for business service.
Vonage has 300 phone numbers / trunk, verizon has 4 phone numbers / trunk. that means that when you dial your vonage number you are about 77 times more likely to get no dial tone on vonage than you are on verizon.
but the other VOIP providers are worse than 300 to 1.