I used it for a couple of years, it’s great if you love customizability and want to run a very clean system. However, the last straw for me was when I needed to edit an image, realized I didn’t had Gimp, so I installed it (which took a long time since I needed to compile it), opened it and it wouldn’t open the image because it was a PNG (I think, or jpg, the specific format doesn’t matter) and that format requires a compilation flag to be enabled, I added that flag globally because why the hell would I not want to have support for it, and recompiled my entire system. By the time I had GIMP able to edit the image I didn’t even remember what I was going to do. I went back to arch not long after that, but always missed defining the packages I want in files to keep the system organized and lean.
I have, in fact I have migrated my home config to nix. The syntax is still a bit weird and still unfamiliar in some cases, especially around the inputs, overlays, etc. Next time I install a system it will definitely be NixOS, currently it’s only running on a backup laptop that I use for testing.