We have not, but I feel we would run into many of the some problems that we had with Nix around version management and interaction with the non-Nix world. Guix looks great if you go all in, but on Railway we don't want our users to have to understand the specifics of how the package manager works, and that becomes difficult with pure solutions like Nix and Guix. That said I'm not too familiar with Guix so could be incorrect on a few things.
