[modulusprime]

I get GSM quality calls on my Nexus 4 (at minimum) via cSIPsimple, pbxes.org, and Google Voice, usually over a mediocre repeated WiFi connection. If there's interest, I'll write it up.

Mild configuration hassle but reliable. Helps to move Google Voice to an account where where you never IM.

[jasonparekh]

I'm interested, please write it up

[modulusprime]

Noted, will do.

[bobmoretti]

As someone who has spent some time tweaking this same setup , with limited success, I'm very interested to hear what you did!