I can see where it might be useful in formal environments and have used nix before sparingly. I found quickly that you need to get in the habit of using the same package manager, when after a few months I couldn't remember how to use a nix package or didn't know how to update a package properly (can't remember exactly what the problem was).
I'm no longer frustrated by not being able to get the same version of a package between versions of ubuntu, not to mention between macos and ubuntu.
I'm no longer frustrated by a package in a repository being updated, breaking me, and not having a way to roll back.
I'm no longer frustrated by software installs being stateful, getting into a bad state, and having to uninstall and reinstall them. You'd be surprised, several times I've discovered that packages auto-update themselves outside of the package manager by overwriting themselves after downloading assets from the internet.
...except I've yet to see this wrapper used anywhere in the industry in professional capacity.
To install it with apt: `sudo apt-get install ffmpeg`
To install it with nix: `nix-env -i ffmpeg-3.4.2`
And then, this whole complicated wrapper shatters.