We are starting to adopt devenv in our team. Overall it's really good--we have control over our toolchain, environment, and the processes that we start. There are some lingering papercuts though, like they haven't yet released a version where they allow specifying the Go toolchain version, and they seem to periodically re-download the Nix package archive. But I think they are improving fairly quickly.
Ultimately, we might still end up moving to straight Nix flakes, just not sure yet.
> they haven't yet released a version where they allow specifying the Go toolchain version
Devenv's maintainers are friendly and responsive when it comes to contributions from downstream, and like 90% of the devenv repo is plain ol' Nix code written in idioms that are common in the community.
I mention it because my team has hit some papercuts as well, but I've been really happy with how easy it's proven to address them. :)