As I understand it, GV uses your mobile minutes to contact the GV server, which then places the call on your behalf. That seems to me that the call would actually be going to the GV server, rather than directly to your wife, and using your regular minutes. Someone please correct me if I'm wrong, but I think this is how it works, and why I have a hard time seeing the value of this service.
100% correct!
The Value for me is that I don't give out my Cellphone or home number, I can manage what calls to take on the weekend or after 5 PM if i want to, I can listen to voicemail while people are leaving it and I never miss a call no matter where I go, All my phones rings at once (home, home office, work, cell, and sometime my GF cell).