Did you have to call LG directly to get your replacement, or was the person at Google able to do it for you? I've called Google a couple times and they've just redirected me to LG, who has said I'd have to pay for a replacement.
I called Google, they issued me an RMA. You basically go back onto the play store and place another order. Rather then being fully charged, it's just authorized. At some point down the road (it's been over a week for me) they ship you a replacement device. You're supposed to return the original device within 21 days of getting the RMA (not receiving the phone).