The main reason I haven't switched my networks to IPv6 is that I plainly don't want to support both protocols at the same time. If I could just switch over to IPv6 and leave v4 behind I would, but I just can't be bothered to do twice the work every time I setup a firewall or a router. Double the config, double the tests and on top of that you have to make sure everything inter-operates smoothly when IPv4 alone still just works.
As you mention in your other post it really is the "billion dollar mistake", it's obvious to me in hindsight that they should have made IPv6 completely backwards compatible with IPv4, no matter the cost. Have a deprecation procedure later on if you want to remove the hacks necessary to support IPv4. Have a clear and simple upgrade path, one step at a time.
Sure, having a clean new standard is compelling but clearly it's making things way more difficult that they ought to be. And that's how we end up more than 20 years after RFC1883 was released with "barely" 20% adoption. NATing was easier than IPv6, so people NAT'ed everything and the internet became the net.
As you mention in your other post it really is the "billion dollar mistake", it's obvious to me in hindsight that they should have made IPv6 completely backwards compatible with IPv4, no matter the cost. Have a deprecation procedure later on if you want to remove the hacks necessary to support IPv4. Have a clear and simple upgrade path, one step at a time.
Sure, having a clean new standard is compelling but clearly it's making things way more difficult that they ought to be. And that's how we end up more than 20 years after RFC1883 was released with "barely" 20% adoption. NATing was easier than IPv6, so people NAT'ed everything and the internet became the net.