Well, I can say (while slow) this does work on my Nokia N97 (firmware v2).
It's more useful at the moment for SMS (as I get charged for outgoing from my carrier).
This makes it free.
Unfortunately the calling works like the JaJah.com system or (using googleVoice's web site directly).
It calls your device and connects the two numbers. This is nice, but won't be fully functional until it can use SIP/over wifi or the like (bypassing the carrier's traditional dial or data service all together).
Great start though! Thanks

not a support question