I think, by default, the focus should be on speeding up Guix (and specifically `guix pull`). I suggest to wrap %default-guix-channel inside channel-with-substitutes-available, like this:
(define %default-channels
(list (channel-with-substitutes-available
%default-guix-channel
"https://ci.guix.gnu.org";)))
This way, beginners would enjoy a little speed-up, and sophisticated
users could still use (list %default-guix-channel).
What do you think?
