It makes the calls using the cellular voice network but it uses the data connection for text messages. At least it did in before I'll check it out first thing tomorrow and report back.
Google Voice installs easily
It integrates with voice dialing
It does send SMS but you need to use the Google Voice App instead of the standard Messaging App to send SMS
I got an error when I was on WiFi that prevented the dialer from working but I think that was due to a WiFi issue
Once I turned WiFi off it worked
If you look at incoming SMS in the standard Messaging App they all show as coming from a 406 number
But it does have the name of the person next to the number and they look better in the Google Voice App