I don't use buildkit for artifacts, but I do like to output images to an OCI Layout so that I can finish some local checks and updates before pushing the image to a registry.

But the real hidden power of buildkit is the ability to swap out the Dockerfile parser. If you want to see that in action, look at this Dockerfile (yes, that's yaml) used for one of their hardened images: https://github.com/docker-hardened-images/catalog/blob/main/...