I mean, yes and no. For an individual or individual systems? No, it's not hard. But I used to oversee a WAN with multiple large sites each with their own complex border, core, and campus plant infrastructure. When you have an environment like that with complex peerings, and onsite and cloud networks it's a bit trickier to introduce dual stack addressing down to the edge. You need a bunch of additional tooling to extend your BGP monitoring, ability to track asynchronous route issues, add route advertisements etc. when you have a large production network to avoid breaking, it's more of a nail biter, because it's not like we have a dev network that is a 1-1 of our physical environment. We have lab equipment, and a virtual implementation of our prod network, but you can only simulate so much.

That being said, we did implement it before most of the rest of the world, in part because I wanted to sell most of our very large IPv4 networks while prices are rising. But it was a real engineering challenge and I was lucky to have the team and resources and time to get it done when it wasn't driving an urgent, short timeline need.