Golden image deployments and netboot have been around for ages. If you want an unified system and control the infrastructure, it doesn't really matter which system you use.

I'm not sure why they chose nix. But it does make it easier to carry local patches than a lot of other systems. I hope they succeed.

The one that makes it trivial to carry over local patches is Gentoo. I carry a set of patches to every new computer and update them whenever neccesary. No overlay yet :P