I think the potential to confuse new users with this enabled by default is higher than without it. Assume that Alice just sent a bug report to Guix, that has been closed or has otherwise been made aware of some bug affecting a software she uses, for which a fix has been pushed. Naturally, she's going to run `guix pull' to test it out, and… not see any difference to the system she currently had.
I think we do have the obligation to clearly document channels-with- substitutes-available and make it so that this particular piece of documentation can easily be found by everyone who is potentially affected by slow-downs. Perhaps we might even want to include an option in the installer to set up /etc/guix/channels.scm to only use channels with available substitutes. But using it as a default without communicating this fact to the users would be a poor idea in my opinion. Regards, Leo
