Good news. On the DSL reports website a report by a OBI competitor shows that they got GV working with Google+ hangouts. See
http://www.dslreports.com/forum/r28323794-They say:We now have a prototype of the GVMate Phone Adapter using Hangouts up and running in the lab with Google Voice that supports both outgoing calling and incoming calling with CNAM caller name display. The same news for using the GVJackApp with a used/expired magicJack dongle.
Update: The one exciting thing found was that you can be signed into the same account at multiple locations and all of them ring when an incoming call arrives. Using Google Chat you could only really be signed in at one location at any given time to reliably receive incoming calls at that location.
Hopefully Obihai is taking notice and will follow suit.