I recently signed up for Obivoice. Quality seems to be very good. I had heard that Anveo has very good quality as well. I would be interested in any feedback from others on this.
Obivoice is better quality than GV and Anveo should be the same or a little better but I don't use it as much to tell.
For incoming all my calls come through GV ringing multiple numbers and you get a bit of a loss of quality doing it that way.
Obivoice is surprisingly good but I am having intermittent problems with 404s and VM pickups and unfortunately most the tshoot has been to tell me to cycle the device or reprogram it.
I have been using GV and Callcentric before and now Vestalink (Obivoice). I feel there is a small delay with Vestalink (compare to Callcentric). Otherwise call quality are almost the same.
I tested Vestalink some, and ended up signing up with Anveo. Call quality on Anveo seems better than Google voice and Vestalink, but I'll admit testing time is still pretty short.