Agreed. One additional thing I do is I have the same setup on my main work workstation and also my old work laptop, so when I do a big swath of package updates (about once a month) I do it on my "scratch monkey" first and make sure nothing obvious breaks. I started doing this after a GNOME update broke my GDM (as you say, until I booted the old generation, but still was a work interruption).

I'm using NixOS "latest" on my workstation, for no particularly good reason.

One success I had was with building up a custom vim setup. I had previously been using Lunar and Astro as an opionated vim distro with LSP+Treesitter and some other "table stakes" things a modern editor should have. But there wasn't a clear way to install Astro in NixOS when I tried it manually. So I just told Claude Code what plugins and settings I wanted in neovim, and now I have a single file that fully describes my vim setup. Before with Astro and Lunar the configs were spread out all over a bunch of files.

I was also able to get Claude Code to bundle up gitbutler-cli, which I wanted to try but so far have not. It builds it from source because there was no existing derivation. It takes a stunningly long time to build, but otherwise it has worked very well in my simple testing of it. Plus, I can build on my powerful laptop and then use that to seed my old, slow ThinkPad T470s and even slower chromebook that I also put my config on.