I'm actively trying to build some cool things with Nix/NixOS and then write up a series of blog posts. Several recent discussions on the Discourse and at NixCon have been focused around Nix/NixOS user experience, at least.
I've recently been building a package set of tip builds of Wayland stuff (sway, screenshot/screenrecord/notification utilities), including instructions for using them on Ubuntu via Nix. I'm also building out a set of packages and modules for Kube/Containerd/Kata-Containers for perfectly repeatable offline-first clusters. I think these two projects can be leveraged to evangelize Nix and NixOS nicely, and dovetails into UX efforts as I build my list of rough spots and fix a number of issues in nixpkgs and random OSS projects along the way.
Also, Gnome-Shell and KDE work perfectly in NixOS anyway, and can be easily made to look just like they do on any other distro... I just recently switched to Sway, coming from KDE (~1.5 years) after GNOME (6+ years?). Not any significant visual differences than when I was using Arch Linux.