At work we use nix+cabal, not nix+stack. Not for any compelling reason other than we've been in business longer than stack has integrated with nix. We have a repo for our consolidated framework that implements our workflow and ops infrastructure parameterized on the project we're building, so we check this in as a submodule in a new project. One thing we do in particular is that we generate nix expressions from cabal files at build time, so we only need to maintain one without updating the other with cabal2nix with every change.
With all this in place in a project, building is as easy as nix-build. Development is as easy as nix-shell. For convenience we have scripts that wrap the workflow for activating a ghci or ghcid shell and some other functions. Deploying to AWS is easy, even though I've never done it myself.
One problem we have is build times with nix. In order to ameliorate this, we have a build server set up with the out of the box nix infrastructure. A developer only needs to build when they make their own changes; within a few minutes of a push the build server will compile the new project derivations and they'll be available to everyone else as binaries. It all Just Works.
As for specifics, the currently implemented Haskell infrastructure in Nix is pretty good. For my personal development I have a few auxiliary scripts a friend of mine cooked up to do very streamlined development. I'm still getting used to it so I can't say much on that front, but it's a very thin wrapper over the stuff in nix. The nix language is really gnarly, but if you can grok it then you can program your build environments in a purely functional way, and that's amazing! I would recommend to every developer that they set up their environment the way they want it. Nix is very flexible and robust. It will handle everything for you, you just need to tell it what you want.
You'll also notice that I put my nix configuration in a shared /home directory instead of /etc/nixos. I think I'm the only person to ever do this because I am neurotic and having to sudo to use version control on my OS config isn't my fave workflow.
