Hi! The NixOS release notes at <http://nixos.org/releases/nixos/16.03-small/nixos-16.03.488.ecf6ca4/manual/release-notes.html> mention that all the ELPA and MELPA packages are now available, which suggests that a fully automated translation works OK (although metadata is largely incomplete at <https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/editors/emacs-modes/elpa-generated.nix>.)
Hence the random thought of the day: Should we try a mass import? Maybe we should change ‘guix import REPO’ to import all of REPO, where applicable? Ludo’.