Network topology isn't really secret under NAT - there are plenty of ways to fingerprint devices based on the packets they send.
I prefer to see my home network as just part of the internet - that way I can let guests use it without compromising my security, and I don't have to worry about vulnerabilities in my router's firmware or physical access to my network cables. IPv6 makes that very easy, because my home network really is just part of the internet.
I do not prefer my home network to be part of the internet. I have insecure devices, things I'm developing or testing, things that third parties have developed. Having my network as a non-addressable space with outbound-only connection forming is a positive for me and I suspect many people.
I hope that as IPv6 takes hold this continues to be the default setup.
Non-addressability does very little for security by itself. E.g. some routers will still route packets from outside that are sent with an internal address as the destination. Make sure you have actual firewalling in place if you're relying on that, and remember that if you're trusting any device connected to your internal network, you're, well, trusting any device connected to your internal network.
> Having my network as a non-addressable space with outbound-only connection forming is a positive for me and I suspect many people.
Most of all, it's probably an illusion. Your web browser has access to your local network, and you probably allow just about any software into your web browser. Yeah, sure, same origin policy and all that. But that doesn't help much with insecure devices or generally crappy software.
A stateful packet filter at the boundary to the public internet still would be a good idea, just without the NAT (which mostly causes complexity, which, if it has any security effect at all, makes it much harder to reason about the correctness of your firewall).
I prefer to see my home network as just part of the internet - that way I can let guests use it without compromising my security, and I don't have to worry about vulnerabilities in my router's firmware or physical access to my network cables. IPv6 makes that very easy, because my home network really is just part of the internet.