as long as the existing packages are enough*, it's really good. if you need to start packaging stuff yourself this is when you'll usually start hitting the pain points (of both Nix the language and the documentation)

*: nixpkgs does have a huge number of packages but that count is massively over-inflated by essentially being a meta-repo that also contains all the language-specific dependencies of it's packages (think pip or npm) and mostly-auto-generated vim plugin packages and whatnot. for things you'd actually want to install "manually" the breadth of the AUR still trumps it in my experience