In my case, adopting Nix was a response to having a poor onboarding process for new engineers. It was always fully automated, but it wasn't reliable before nix. So somebody would join the team, and it was embarrassing because the first day would be them troubleshooting a complex build process to get it to work on their machine. Not a great first impression.

So I adopted Nix "in anger" and now new machines always build successfully on the first try.

For me it was easy to set up. 80% done on the first day. It helped that I understood the conceptual model and benefits first. There's a lot of directions you can take it, I'd recommend getting something really simple working then iterating. Don't try to build the Sistine Chapel with all the different things integrated on day one.

It's hard to overstate how well that decision has worked out for me. Computers used to stress me out a lot more because of dependencies and broken builds. Now I have a much healthier relationship with computers.