it kind of 'just works' if someone already wrote the nix code to do what you want it to do and put it in nixpkgs and you manage to find it and figure out how to use it. but if that isn't the case, good luck. i once spent almost a week trying to get a program to build and run properly under nix that could probably be installed in around 20 seconds on a osx/windows machine.
The quality of the managed / packages software, however, is still a bit subpar compared to Debian and Redhat.