I am now at NixOS. I like the reproducibility and immutability of the distro, but the documentation is far from great and configuring the OS you want is not that straightforward. I also don't like that even though it has a great number of packages, they tend to be slightly outdated.
I am not sure if I will stick with it, but I really like that I can create very specialised configurations that are also portable. I am currently using KDE but I am thinking of switching to Hyprland once I get more comfortable around NixOS and home manager/flakes, as nothing beats tiling managers in my opinion.
After trying out a few distros over the last 20 years or so (openSUSE, Ubuntu, Debian, Arch, Fedora and Silverblue were the ones I actively used for a stretch of time on desktop, Debian and CentOS on server), I also landed on NixOS.
Who knows what the future brings, but things feel more settled to me than they ever have. Maybe that's because there's a (declarative) solution for every custom setup, it's just a function of time and profiency in Nix. Or maybe it's because I invested quite a bit of work into a trivially reproducible setup for most of my machines and workflows (all in one glorious version-controlled flake), that the sunk costs are too high to switch elsewhere.
I'm still willing to experiment with DEs/WMs, currently running Gnome on my main and Sway on weaker machines. Hyprland is a bit out there for my taste, but I'm really looking forward to giving Cosmic DE a try once it's ready.
Yeah, NixOS really does not have good documentation to get you started. But once you have a system installed and you start tweaking it, it's pretty easy.
I would argue that NixOS is the most up to date OS, though. obviously you don't get new software on the stable channels, but you can always pull individual packages from unstable if needed without breaking the whole system. Most software on unstable updates insanely fast, even faster than Arch Linux. The multiple days of delay for Hydra to run is a bit annoying, though.
It is frustrating when some of the more niche software doesn't get updated on time, though, one of the downsides of having the single biggest Linux package repository in the world. It's made worse by the fact that you can't just install a 3rd party deb or rpm without some know-how.
You can get pretty far with copy-pasting. If you want to try it out, you should first realize that there's always 10+ different ways to do the same thing. Stick with what works and with what seems the most intuitive to you.
Personally, I suggest going straight for a flake-based setup. Flakes are somehow still labeled experimental, but they're actually mature and broadly adopted.