Hi,

Nix has a feature called "channels".  To quote the docs, "a channel is a
Nix mechanism for distributing Nix expressions and associated binaries"
[1].  It sounds like this includes the nix tools like "nix-build", but
I'm not sure.  In any case, it's clearly similar to "guix pull", but at
first blush channels seems more featureful and more useful.  Here are
some features:

* A user can "subscribe" [2] to multiple channels ("stable", "unstable",
  etc.).

* "Correctness: The channel is only updated to a new revision of
  NixOS/Nixpkgs if it passes certain tests" [3].

* "Efficiency: The channel is only updated after all Hydra builds in
  that revision have finished, *and* all binaries have been mirrored"
  [3].

* "In principle, you can do rollbacks on the channels profile ("nix-env
  -p /nix/var/nix/profiles/per-user/root/channels --rollback") if you
  don't like the result of a 'nix-channel --update'" [3].

These all sound like features which would be nice to have in Guix, so I
wonder: why doesn't Guix have "channels", too?

For more information about Nix channels, see here (Eelco's thesis [4]
includes more technical details - search it for the word "channel"):

[1] https://nixos.org/nixos/manual/#sec-upgrading
[2] https://nixos.org/nix/manual/#sec-channels
[3] https://nixos.org/wiki/Install/remove_software#nix-channels
[4] http://nixos.org/%7Eeelco/pubs/phd-thesis.pdf

-- 
Chris