Here's why I don't like Homebrew, and why I believe Nix is (almost) strictly an improvement over it: 1. Updating packages is not safe. If I update openssl and

Here's why I don't like Homebrew, and why I believe Nix is (almost) strictly an improvement over it: 1. Updating packages is not safe. If I update openssl and the ABI changes, all of my currently installed packages that depend on it are now broken -- time to rebuild everything. I've burned way too many hours on ABI breakage and rebuilding everything. That problem can't happen with Nix because Nix will ensure that each library is linked precisely to the versions of the libs they need. 2. Nix has a continuous integration server (called Hydra[1]) that builds every package, and caches the binaries. Because Nix knows each packages entire dependency graph, Hydra only needs to build just the packages that have changed. When I want to update some packages, I can count on not having to rebuild everything myself. Each binary package is signed, so I know my stuff is coming from the build server, regardless of whether or not I get the files through a cache or third party. I can also run my own Hydra instance to build my OS X and Linux packages, and I can share the binaries with others should I wish. 3. The lack of determinism. With Nix on OS X, packages are built using OS X's native Sandbox APIs to ensure that the build process can only see the dependencies that were explicitly specified. This guarantees that if the build works on my machine, it will work on yours -- whereas I've seen brew formulas under-specify configure flags and such, resulting in the default of linking to non brew installed libraries, causing quite a bit of confusion when things don't work at run time, or just flat out fail to build. 4. Brew is OS X specific. Nix works on OS X, Linux, and a FreeBSD. As someone who deploys to Linux virtual servers, it's nice that I can use the same versions of packages both in development and production. It's not all roses, though. We have a smaller community of OS X users at this point, so not everything works (thus my "almost" qualification). Regarding the underlying tech and the outlook for the future, Nix is a superior tool.