Hi! I very much agree with what David wrote.
Note that NixOS has been merged into Nixpkgs several months ago precisely for the reasons David gave. That Nix remains separate from Nixpkgs/NixOS can be problematic because as new features of Nix language get used in Nixpkgs, backward-compatibility is broken (and adding features to the language is not uncommon since Nix is an external DSL that becomes less and less DS, as is often the case with DSLs ;-)). Ludo’.
