We're using it in the same way - running NixOS on robots.
Overall I think it is succeeding, though it definitely doesn't 'just work' out of the box. We've invested a fair bit of effort into things like:
- containerised services[1]
- UI for branch deployment/service management
- delta patching (at the byte level, to save bandwidth)
The main problem was always that nixlang/nixpkgs are arcane and have a steep learning curve. The majority of your colleagues (in any workplace) don't care about build systems and just want things to work. I think that has been more or less solved by LLMs, and it's now more viable than ever to adopt Nix.