I'm a huge fan of Nix, and I'm glad to have stuck with the often times daunting process of getting into it - and I have to agree with the author's point regarding the documentation. That's not a fault of the people who actually did sit down and document their process, or distill their learning path into a tutorial - I myself understand it well enough to use it, but not well enough to really explain it without confusing people even more, but it's still a pity that finding good, exhaustive documentation for Nix is really difficult.

Another pitfall is the usage of flakes, which, on the one hand are (imho) great, recommended everywhere and often times even assumed to be used implicitly, but on the other hand are still experimental. I myself started using flakes not because of the promised benefit (although I did realize the benefit later on) but just because multiple tutorials I've read gave me the feeling that flakes were the de facto way to do Nix from now on - and mind you, that was in late 2020.

I'm using Nix for setting up my work machine (Mac via nix-darwin), my private machines (NixOS), selfhosting that's not in my k8s (also NixOS), and some private projects (dependencies, ci, and containers) - where the issues I've described don't really bother me, but for professional projects, where I'd have to convince and/or instruct colleagues, Nix feels a bit too rough around the edges for me right now.

Edit: I also think it's important to distinguish between Nix the technology (fantastic) and Nix the language (meh) - which is why I'm still itching to try out Guix[1], which is similar to Nix (the technology) in a lot of ways while using Guile[2] as a language.

[1] https://guix.gnu.org/

[2] https://www.gnu.org/software/guile/