This was my experience at Google as well. I was there a little over five years. There were times when I was completely in love with my team and my project and I was working until 3AM and feeling great about what I was getting done. There were times when I was burnt out or dealing with personal/medical issues and not contributing nearly that much. I can't complain about how I was treated in either circumstance.

Beyond my own experience, I had multiple teammates who had long commutes and family commitments and made a rigid practice of leaving before five every single day. As far as I know, none of them were ever given any trouble about it. Maybe they weren't promoted as fast as if they'd burned the midnight oil, but that seems like a fair trade.