I am sure one can find some usecase for NAT66. Things like proxy servers are not dead either. Or load balancers. It all does the same job of redirecting traffic from one IP address to another.
BUT - the article is dead wrong about the small office with multiple internet connections. The answer in this case is much much simpler: Attach two routers to the network; DONE. Its that simple. It will work. No NAT66 needed.
With IPv6 both routers will announce themselves to the network. All computers will pick up two addresses, one for each router. All computers will continuously monitor the health of each router and within 30 seconds of a failure switch to the other.
And yes, the office printer will also just work. The software knows about the automatic renumbering, it is smart enough to use link local addressing, which never changes, for talking to the printer. And using multicast for device discovery on the network.
What about serving content to the public internet? The author links to a convoluted IPv4 NAT solution which does not provide a good solution for that either. Currently the only way to be true multihomed as a content provider is to use BGP - the same for both IPv4 and IPv6. But this is changing with the LISP proposal: http://www.lisp4.net/
I believe LISP will basically solve everything the author is complaining about. No it is not mature yet, neither is NAT66 really. LISP is a MUCH nicer solution however with many other benefits too.
Biting the hand that feeds IT
