more information to (1), the physical number must be registered with google voice, which is required by google.

I tried it on Nokia 5800. It works well. I registered this account to say thank you, and want to request more features :)
(1) gizmo5 number support. If I set my number to gizmo5 number, it won't dial it. It does work if I set it to a physical phone number.
(2) When manually entering a phone number to call, no more than 10 digit can be accepted. One importance feature of Google voice is its cheap international call. I need enter more than 10 digit to do that. I haven't tried whether it works if the number in the contact exceeds 10 digit.

For now, I still have to log into my Google voice account through web, to ring my gizmo5 number, or/and to make an international call. Could you please add those features in your next release?

A good software, Thank you!