How many years since Google bought the GrandCentral and renamed it to Google Voice? But the great news is: the new Hangouts Dialer released just today now let you place and receive calls with your GV #.
You also need to install or update Hangouts to the latest version 2.1.2, released just today too. Furthermore, you also need to install or update Google Play Services to the latest version 4.4.52.
If you have multiple GV accounts, you may add them all to your phone. Then you can
pick any one of them at anytime for calling out, just like what you do with
multiple GMail accounts.
Receiving calls is not enabled by default, you need to enable it if you want that for your account(s). So is SMS.
Call quality is very good over a 3G (Sprint EVDO) connection, sounds like GSM codec to me (not so sure).
To make this matter even sweeter: International calling rate is lowered down from $0.02/min to $0.01/min for some countries including China.
If you still need Google Voice in an alternative and more versatile way, consider KoT VOIP.
[update] Hangouts turns out to be not dependable, suffering from the same problem like Acrobits and Talkatone: