On Ubuntu I felt that command-not-found was always too slow and always telling me things I already knew. On NixOS I love it. It's instant[0] and I really don't know where some things are[1] -- finding things in NixOS is a bit harder as there's no good equivalent of apt-file.

[0] Is this just some kind of bias because I find it useful? I don't think so. On a pretty beefy laptop I would wait a second or more for a command to return, but on this decade-old 4G RAM machine I'm getting "[hey maybe you should nix-env -iA nixos.bazaar?]" immediately. Maybe I have less things in my PATH? Maybe the NixOS c-n-f db is smaller? No idea.

[1] I've used nixpkgs for a year and I've been on NixOS for two weeks. I was on Ubuntu since 2004 and on Debian since 1998. Also, I admit that nixpkgs package naming is not optimal when it comes to consistency.