Comment by tombert
The reason I keep it around on my laptop is mostly because of the snapshotting.
I generally do know my way around Linux command line nowadays, but with Ubuntu and Arch (especially early in my career when I didn't know what I was doing), I would get into states that break the video driver, or break GRUB, or make the machine unstable, and the only thing I could do was reinstall the whole OS.
With NixOS, since it's all declarative, if I end up really breaking something, I can always reboot and choose a previous generation. It makes things a lot less scary for me, I can experiment with and play with different boot parameters and drivers and I know that I won't be stuck spending two hours reinstalling everything. It changes the entire way that I work.
For example, on my current laptop (Lenovo Thinkpad, AMD), I was having an issue with my USB ports idling out, so sometimes the first ~4 seconds of my typing wasn't registering since the USB port had to wake up. The solution involved adding a kernel parameter `usbcore.autosuspend=-1`.
Had this been something like Ubuntu, I have been burned enough trying to add kernel params that I might honestly have just lived with the annoyance because I didn't want to risk everything breaking, but because I knew that there was no actual risk with NixOS, I was able to fix it permanently, and I have the solution committed to Git if I ever have to do this on another computer.
Just a side note for those who aren't on NixOS, but who would like 90% of snapshotting: use timeshift. Especially if your file system is BTRFS. It'll do daily snapshots of all your system files, going back 5 days by default. I've only had to use it once, but it was invaluable. Another nice thing is it's very much a set-and-forget program.