I probably appeals most to developers as sharing application development environments with shell nix files is totally awesome.
I must say that using nix on my primary workstation makes it feel like an appliance. The system generation roll-back have saved me a lot of times when an application update brings a regression.
That makes sense, I never need to share my config with anyone else.
Also I love the ability to mix packages with source compiled software, which is one of the reasons I use FreeBSD on my primary desktop. It does that combo really well with its ports collection.
I feel like FreeBSD is almost this middle ground between a typical package managed (?) system and something like Nix. I didn't wind up needing that middle ground, but just the few months I spent with it made it clear how well-designed it is. Only on Nix have I written and modified my own packages that much, and that's partly out of necessity.
That's true actually, the rc.conf file is a little bit Nix-like. It's basically a single file for all your configuration. Never thought of it that way.
Many applications don't obey it though. Makes sense because they'd have to make code specifically for FreeBSD and its marketshare is tiny.
I must say that using nix on my primary workstation makes it feel like an appliance. The system generation roll-back have saved me a lot of times when an application update brings a regression.