I've had an amazing time with it so far. It's so easy to package for (I haven't contributed a package upstream, but I'm working on it). There's like two places you put your configs (/etc/config.scm and .config/guix) and it all just works. Like, I'm not even an emacs user, I don't really use Lisp much, but it's just such a pleasure to work with. I haven't really had any issues with firmware or anything proprietary (old thinkpads ftw), but nonguix and flatpak exist to fix that.
Really the only issue I have is that some software is behind by a version or two, and some things I use haven't been put in the channel yet (but it seems everything I use regularly is either a patch being worked on or already working).
It took a little bit for it all to click, but after finding the cookbook and looking through others configs, it made a lot of sense.
All that said, I'm a bit too committed to Arch to switch my main machine. Hopefully soon though.
NixOS has much more packages, and they are more up to date. Honestly, it is a shame because there are many things about Guix I prefer (especially its license). Also, if you are a developer, it is really nice getting to use nix flakes to set up your development environments.