Wait... does this mean you can finally get texts/voice mails from two GV accounts on one device!?
I have not gotten the 'blue conversion box' (migrate google voice to hangouts) yet so I couldn't test this myself, but technically, yes!
Anyway, I dug around the settings and found the 'ring phone when incoming voice call' checkbox that is unchecked by default, so when this box is checked this means a huge YES to my question above! I am confirming that now you can both make outgoing calls and receive incoming calls on your GV number, 100% over data connection. This also allows you to receive and make calls using multiple GV numbers, by adding multiple Google accounts to your phone.
I really like the new interface, too. It's slick! :wub:
Some clarification:
I'm still not sure what the 'hangouts dialer' is and why it was rolled out this way. It's a stand alone app but it was just adding a dialer tab to the Hangouts app. After you installed it, you simply just fire up the Hangouts app and there's a dialer tab right there, you don't have to actually fire the dialer app to dial out.
Be aware that if you have 'ring hangouts for incoming GV call' box checked and also have your GV sets to forward calls to your actual (SIM card) number, then both your phone and Hangouts will ring when someone calls your GV number. This is the standard behavior similar to when you have an app like GrooVeIP or the like, so some people may choose to just turn off forwarding and always receive their calls over data than through the cellular network (or vice versa). I personally would like the option to automate so it would ring the phone through forwarding by default, but ring Hangouts if there's no/weak cellular signal (but there's WiFi).