I do, yes. I’d love to use it, because I like Scheme a whole lot more than Nix (I hate Nix, the language), but Guix suffers from a few shortcomings that make it unsuitable for my needs:

• There’s no systemd. This is a deal breaker, because I built plenty of stuff on top of systemd, and have no desire to switch to anything else, unless it supports all the things I use systemd for (Shepherd does not).
• There’s a lot less packages, and what they have, are usually more out of date than on nixpkgs.
• Being a GNU project, using non-free software is a tad awkward (I can live with this, there isn’t much non-free software I use, and the few I do, I can take care of myself).
• Last time I checked, they used an e-mail based patch workflow, and that’s not something I’m willing to deal with. Not a big deal, because I don’t need to be able to contribute - but it would be nice if I could, if I wanted to. (I don’t contribute to nixpkgs either, but due to political reasons, not technical ones - Guix would be the opposite). If they move to Codeberg, or their own forge, this will be a solved issue, though.

Before I switched from Debian to NixOS, I experimented with Guix for a good few months, and ultimately decided to go with NixOS instead, despite not liking Nix. Guix’s shortcomings were just too severe for my use cases.

NixOS, because:

• I can have my entire system be declaratively configured, and not as a yaml soup bolted onto a random distro.
• I can trivially separate the OS, and the data (thanks, impermanence)
• it has a buttload of packages and integration modules
• it is mostly reproducible

All of these combined means my backups are simple (just snapshot /persist, with a few dirs excluded, and restic them to N places) and reliable. The systems all have that newly installed feel, because there is zero cruft accumulating.

And with the declarative config being tangled out from a literate Org Roam garden, I have tremendous, and up to date documentation too. Declarative config + literate programmung work really well together, amg give me immense power.