It's cool to see the integration finally. A couple of things to note though:
(I'm on Sprint, so my GV number is my carrier number. That may affect these observations.)
I can set the Hangouts app to show incoming calls to my GV (Sprint number) number and it does ring on incoming calls. However, if I decline a call, the built in Android dialer then begins to ring and I have to decline it a second time.
If I want to record an incoming call, I have to answer using the Android dialer. Answering with the Hangouts dialer and pressing 4 does nothing.
Same result for conferencing. If I want to conference a call, I have to initiate or answer a call with the Android dialer.
