Yeah. We've used it on servers. It's good in a small setting where a handful of Nix experts can run the infrastructure show.

Getting it to scale to an organisation of hundreds wasn't feasible. As soon as we needed to start expanding "infrastructure" beyond just one team, and rapidly hiring new engineers in the context of rapid growth. Training and learning curve was intractable. And we cannot just easily hire NixOS experts like traditional Ubuntu OS.

Nix made complicated things possible but simple things complicated. Pretty much every new feature request could only be processed by a handful of Nix experts, and it was obvious that wouldn't scale with the growth of the company.

Frankly, Nix solves problems that the industry has already solved or knows how to live. Its lack of adoption from software vendors makes the economical cost/benefit unatractive.