1. Got Gizmo5 and Google Voice accounts
2. Added Gizmo5 SIP number to my Google Voice's list of registered phones
3. Calling the Google Voice number rings my N770 with the Gizmo5 client running, as expected
4. Added Google Voice username and password to Gizmo5 (to receive/make free calls with Gizmo5 via Google Voice)
5. Gizmo5 call-out to a U.S. landline gets me a message to buy call-out credits for Gizmo5

Registering my Gizmo5 SIP number with Google Voice gets me free call-in, correct? There's no need to register my Google Voice account with Gizmo5 if call-in is all I want?

Registering my Google Voice account with Gizmo5, in theory, would get me free call-out? (Even if it's limited to 3 minutes, that's enough to contact someone for him/her to get his/her computer up for tablet-to-computer calls.)