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I was looking at that, too. It seems there are now two voice options. The 'calls' panel was already there, for connecting to phone numbers. But if you click the ... next to an open text chat window, there is an 'audio' next to video and mute that I don't recall seeing before. So audio paired with typing, independent of the phone network, more like standard Skype.
 
It's weird. You can't add someone to the Hangouts contact list (and subsequently the Favorites list) unless they're on Google as far as I can tell. And you have to do a Facebooky sort of friending to add them.

It does have a messed up version of the iOS contacts list in there if you go through a few buttons.
 
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