Only drawback-it's available in tri-state (NJ, NY and CT) area. Call quality is as good as copper line phone. I have used Lingo, sunRocket and Optimum Online-believe me-this is the best VOIP phone service. They provide their own adapter free of cost. Service is available only to those customers who has cablevision but it's really excellent.

I have 2 VOIP lines, 1 with Optimum Online, 1 with Sunrocket. I've had Optimum Online for about a year and in almost every respect it's as good as a wire line, but cheaper. The Sunrocket line is cheaper yet, but with more compromises. If you live in Cablevision territory I recommend you stop throwing away money with Verizon, Cablevision is half the price and just as good. The only real downside is that they wouldn't sell me a second line without me paying for a second cable modem, hence I added Sunrocket for the second line. I now have 3 phone lines (I work at home), 1 Verizon copper line, 1 Optimum line, and 1 Sunrocket line. The Verizon hardware works much better than Sunrocket, and the voice quality is excellent. I use the Optimum line for FAX and to make calls, works without a hitch for both. Voice quality is equal to my copper line. The Sunrocket adaptor has problems with my phones and wiring, I've got a lot of work to do there. All in all, if I could get a second Optimum line I'd do it rather than Sunrocket, although the Sunrocket line is cheaper. Verizon has good service, but international calling is extremely expensive on their standard plans (read I got nailed for 1.35 per minute!) and the overall bill is more than twice Optimum. Sunrocket is 2/3 of Cablevision with really good international rates to boot. Recommended, but only if you are willing to deal with wireless phones. If you live where your can get Optimum Online, it's a bit more expensive, but higher quality. Either is a better deal than Verizon (I can put in a PBX to deal with the line issues and the payoff is short, the Sunrocket line is about $50 per month cheaper than Verizon).

No problems since day one. Excellent sound quality. I like that it has E911. I dont like that it doesnt include calls to American terrorities (puerto rico, guam, etc.). I would recommend this service to everyone. Service is only for cablevision customers.