Anybody using it extensively? It doesn't seem to have made the splash I expected it to at launch

I used the old CUE-based version when it came out, and was really excited about it. I liked it, and enjoyed working with CUE, but the API was clunky and incomplete.

Then they completely abandoned not just the CUE frontend, but CUE altogether (while strenuously denying that they were doing so) for a GraphQL-based rewrite that focused on letting people use popular general-purpose languages to construct their workflows. The initial rollout of this was not feature complete and only supported imperative languages (Python and TypeScript, IIRC), which I didn't like.

Instead of porting everything over to all their new interfaces, I hopped off the train and rewrote all of our portable pipeline scripts in Nix, via Devenv. At the time, I'd never used Devenv before, but getting the work done that time still took maybe a tenth of the time or less. More than anything else, this was due to not having to fuck around with the additional overhead Docker entails (fussing with mount points, passing files from one stage to another, rebuilding images, setting up VMs... all of it). I got the reproducibility without the extra bullshit, and got to work with interfaces that have proven much more stable.

I still think there's a place for something like Dagger, focused just on CI, perhaps even still using Docker as a deployment/distribution strategy. But I no longer trust Dagger to execute on that. I think a proper external DSL (probably special-purposw but still Turing-complete, e.g., Nickel) is the right fit for this domain, and that it should support multiple means of achieving repeatability rather than just Docker (e.g., Nix on bare metal and Podman, to start). An option to work on bare metal via reproducible environment management tools like Nix, Guix, or Spack is a valuable alternative to burdensome approaches like containers.

I haven't looked at Dagger in several months, but the other big piece that is missing for portable CI workflows is a library that abstracts over popular CI platforms so you can easily configure pull/merge request pipelines without worrying about the implementation details like what environment variables each platform exposes to indicate source and target branch.

Idk anything about all the AI horseshit; I was off the Dagger bandwagon before they took that turn. I don't know if it's serious or a nominal play to court investors. But that kind of pivot is another reason not to build core infra on top of the work of startups imo. If the product is 70% of what you want, you have no way of knowing whether filling that 30% gap is something the maintainers will suddenly pivot away from, even if their current direction looks aligned with yours.

I'd recommend considering tools in this space only if (a) they're already close to 100% of what you need and (b) they're open-source. Maybe you can relax (a) if it's really easy to extend the codebase (I find this to be true for Devenv's Nix modules, for example.)