They took a lot of inspiration from NixOS[1], which many people successfully use and it isn't in beta (not meant to badmouth GuixSD of their efforts, just wanted to put it out there)
Many people pointed out that NixOS has been discussed here many times already, but nobody mentioned Guix, so here it is, for reference: https://news.ycombinator.com/item?id=9127679
I was going to cite Nix in response to this article, but I see you have already mentioned Guix. I hope that both GuixSD and NixOS strike happy balances between the two opposing philosophies described in this article.
I've mostly used NixOS, but eyed Guix from time to time, not really dipped my toes into the Guix-water yet but not completely unwilling either, the syntax and cohesion is really interesting and alluring when compared to NixOS.
I have the two threads favorites (sub-threads in a large conversation) that might be of interest to you:
[1] https://nixos.org/
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