I've been a RingTo customer since buying my OBi 200 in July. At the time it looked as if Google Voice was on it's way out. Didn't turn out that way but I have no regrets going with RingTo. Call quality has been generally excellent.
Like John, I found the porting process to be painless. The service is rapidly evolving and they are most definitely listening to their customers. In addition to using the service on my OBi, I'm beta testing both their iOS and Android mobile apps. I think you'll like the direction those apps are going in. It will take a while for them to implement all the features requested by customers, some of which are currently offered by providers such as Anveo, Callcentric and
VoIP.ms. That said, it's hard to beat free and I think they stack up quite nicely with Google Voice.
Regarding the 911 requirement. RingTo is a service of
Bandwidth.com, a regulated telephone company (CLEC). Given the regulatory environment they operate in, they made a business decision to require 911 service with an OBi. Most service providers are not related to CLECs. As a result, some are more flexible regarding 911. Callcentric is related to a CLEC (Telengy) and like RingTo requires 911 unless you tell them you're using their services outside the U.S. My understanding is that the choice of Anveo as the partner providing 911 was Obihai's.
Regarding you're existing 911 service with Anveo, I'm not sure it will work with RingTo. As registered on my OBi, the service reads as Anveo E911 for RingTo. The for RingTo part may be important. Seemingly, if that's the case, opening a ticket with Anveo ought to be able to get things sorted out.
One of the best ways to get a better feel for RingTo is to visit
community.ring.to.