There is a similar question on the site which must not be named.
My question still has a little different spin:
It seems to me that one of the biggest selling points of Nix is basically infrastructure as code. (Of course being immutable etc. is nice by itself.)
I wonder now, how big the delta is for people like me: All my desktops/servers are based on Debian stable with heavy customization, but 100% automated via Ansible. It seems to me, that a lot of the vocal Nix user (fans) switched from a pet desktop and discover IaC via Nix, and that they are in the end raving about IaC (which Nix might or might not be a good vehicle for).
When I gave Silverblue a try, I totally loved it, but then to configure it for my needs, I basically would have needed to configure the host system, some containers ans overlays to replicate my Debian setup, so for me it seemed like too much effort to arrive nearly at where I started. (And of course I can use distrobox/podman and have containerized environments on Debian w/o trouble.)
Am I missing something?
I switched from a big custom Ansible deployment to NixOS.
The system includes 8 managed machines, multiple VPNs and a custom certificate authority.
Downsides:
Still, I can only tell you how much more at ease I feel with the NixOS based system. Its just much easier to refactor, not having to take care of legacy cleanup and polluting the machines over time.
Once you wrap your head around it all more complex system architectures start to become manageable/maintainable.
IaC
You still need sth like Terraform on the side for your actual infrastructure provisioning.
Solutions to bridge this with the Nix ecosystem are evolving in the nix-community repos on Github, but I found it easier to manage that separately for the time being.
All in all I would recommend NixOS based systems for the heavy lifters in your setup. If you want to deploy a fleet of machines you are entering new territory. Exciting, but maybe too much of a time commitment for some.