I looked closely at Nix and there is a lot to like there. The thing that turned me off is that it is just too complex. Going from something like Dockerfiles to Nix is just a huge leap.

Example: http://sandervanderburg.blogspot.com/2014/07/managing-privat...

A lesson from Docker is that we have to make this dead simple. It has to be something you can grok in 15-60m.