NAT does little to nothing for security. NAT != firewall, and if your security depends on keeping internal IPs secret you have a problem. You can easily firewall without NAT.
Now I do agree that my point was kind of moot because it's indeed easy to firewall without NAT. I am all for IPv6 if it's done well. I especially like the idea of finally moving away from ARP Spoofing attacks thanks to Neighbor Discovery (ND).