It was anti-climactic and worked so well as to be boring, which is the absolute highest compliment that a replacement and cutover can have.
I doubt I have anywhere near the networking knowledge you have, so some of the more complex things I have set up; like my BGP routes for my Kubernetes clusters and my VLANs/trunks etc, that have taken a lot of tinkering might take me quite some time. I expect the way they're configured will be different, terminology might be different, and of course the UI will be different, so I can't just do it by reference.
I have no problem taking my time, so long as we have the basic networking we need for family and working from home.
Those things work the same way in opnsense. Most of my conversion was just data entry of the particulars.
I try to keep my main fws as simple as I can, for the benefit of the household, but I do get carried away with home automation and IaC/CM to my firewalls.