There are number of people not really sure about what is Google voice. It is a virtual number online that you can call and configure the device that you wish to receive the call. For example, you can configure it to receive phone call from family member to ring your mobile phone as well as your work place. This virtual number will not change and you can update the latest mobile number if you change your service provider. Is a good service but seem like duplication to current iPhone function.
I would like to say that Google have been forgotten who is the master of his business model. They earn money through advertisement and who is the boss now? Apple is the one who put up the adv and yet they trying to bite back. Joking man