[mercurial]

> I was too lazy to do things properly (kickstart script, etc.) so I have a bash script with about 10 "apt-get install" lines that set up everything I want on Ubuntu or debian, and a few more "echo" lines that configure 90% of my other preferences.

You can do even better than that with NixOS: the system configuration is a single file (though it's possible to split it into different files). The file contains, if you use the declarative system-wide installation system, the list of all non-default software and their non-default configuration. If you copy the file to your new system and use "nixos-rebuild switch", everything will be downloaded and configured correctly.