A user testimonial of sorts...:
My S.O. is using CircleNet with their DID offer for both inbound & outbound on an Android phone via Wifi only - and she is thrilled with it thus far.
It seems to be fully reliable and the sound quality is excellent.
(I have an Obi110 and am also a CircleNet user but only for outbound at this time until/unless my Obi stops working with GV...and I am also quite happy with the quality & reliability of CircleNet.)
A side note worthy of mention IMO:
There does not appear to be any provision for voicemail with the CircleNet DID, so what I did with her phone was to forward her GV number to the CircleNet DID - thus gaining the use of the GV VM.
There is also no SMS feature with the CircleNet services, so...
Since her phone is not using any cellular carrier at all, using some clever Android tricks I was able to find via searching, her phone now uses Acrobits as the default dialer and GV as the default SMS provider - and all 100% via Wifi - but the backbone which holds all this together is the really good phone service from CircleNet and we both recommend it quite highly.