I've been using devenv for new projects. I like it so far. Some might find nix (which it requires) to be overkill, but I think that's underestimating how devilish of a problem it's solving.
I'd be cautious about thinking that you'll be able to use it for complex projects without eventually needing to enter the NixOS rabbit hole. This hasn't happened to me yet on a project that I'm using devnenv with, but while using nix flakes I've found weirdness in nipkgs that I wanted to address.
On the other hand, the ability to put non python deps in a place that feels like a venv... feels pretty magical.
Yes for Python it seems to sit between a blurry midpoint of "just use Poetry!" and "just use a container!", but I can see it potentially being useful for a batteries-included devenv in more niche applications like Julia, Elixir, microcontrollers/development boards, etc.
