Google Voice: If you initiate and receive all calls on your cell phone with Google voice as a default, are you using cell phone minutes or is it counted against your data plan?

Receiving calls on your phone via Google Voice is generally done with call forwarding in the background, hence you'll use voice minutes for those calls. Also making calls via Google Voice uses your phone's voice plan to dial a central number as well and then call out from there or will call you with the call. Google recently acquired Gizmo so may integrate some more VoIP functionality later, but as of now, the first or last bit of the call happens over your regular cell phone voice plan.