After using Nix and NixOps, my sense was that a Nix package manager module for puppet&co would be really really useful. With NixOps, my concern was that I need to have a trusted OS, and I didn't feel comfortable having to use a custom build of something Ubuntu-ish.
Maybe there's a way to convert or bootstrap any Linux OS into a NixOps-compatible distro. But I didn't see anything.
Basically Nix obsoletes much of Puppet&co, to the extend that you probably want to go without it.
On top of that Nix also provides great means for deployment.