I've been a VOIPo user since I began beta testing the service in February 2007. I eventually ported over my Packet8 line (a number ported from Vonage). I simply have no complaints. The sevice works, and I do not have to really think about it. Its there when I need it. They do have some cool features like call recording, and caller ID filtering. Even for new users, there are good deals for 1 and 2 year sign-ups. If you think monthly is a safer bet, quiting the yearly plan early will simplycost the monthly price after the 30 day money-back period. In other words, there is no real risk in a long-term sign-up other than saving more money if you stick with it.
For those that like a BYOD setup, they do offer credentials to setup a different device like a soft phone or a different ATA. As for support, BYOD is only a user supported service. The supplied device is the acid test to prove the service works. Even so, many people use alternet devices, or a soft phone to act as a second line in a different location - or while they travel.
VOIPo's biggest weakness is their documentation, and web interface. Nothing is difficult, but it may slow you down discovering all the great things. They are working on both documentation, and an improved web portal, but they both have been a long time coming. VOIPo is great at innovating, but they do take their time trying to ensure new features do not affect the core service. They are not afraid to spend more time and money versus rushing a feature because it would boost sales.
I also understand VOIPo is profitable. It took Vonage a magnatude longer to approach break even. VOIPo has an effective set of plans that work for the customer, and in the business sense. VOIPo will be around a long time! They are growing fast, and their technology scales well to demand.
Although I've beta tested VOIPo, I am simply a long time user, and make no income from my enthusiam. I happily reccomend VOIPo to all considering a plug&play VoIP service. I began with Vonage in January 2003 (And some experimentation with iConnectHere from Delta3 December 2002.)
My home on the Interenet is DSLReports.com in many forums including the VoIP Tech Chat Forum - be sure to check it out! That is where I first heard of Vonage, Packet8 and many other providers. That is where I learned way back that I could beta test VOIPo. I resisted the VOIPo chatter for many months before giving them a better look. I am so glad I did! It has been the best experience of all my VoIP choices (And I beta tested the Vonage V-Phone too!)